HW#45 JSON Decoder

 Dawei

Published in

彼得潘的 Swift iOS / Flutter App 開發教室

48 min readMar 17, 2024

這次的練習主要是練習如何解析JSON的資料，並建構以下內容為這次練習的API(打星號，是稍微複雜一點的API資料庫):

REST Country 🌟
REST GitHubs
Trivia API
Apple Marketing RSS
Random User Generator 🌟
Joker API
iTunes API 🌟
YouBike API

這次練習的內容，主要是為了練習如何解析大量的JSON file，下列內容是參考彼得潘的文章內容做學習。

練習主題:

新手的 Swift JSON decode 練習題

搭配 AI 建立自己感興趣的 JSON API

medium.com

使用 Postman 研究 API & 產生 Swift 程式

在開始撰寫 Swift 程式串接後台的 API 前，最好先利用一些工具確認後台功能是否正常，以及檢查對方回傳的 JSON 資料格式。如果發現後台有 bug，我們 App 工程師就可以先去買個下午茶休息一下了。

medium.com

iOS 解碼 & 編碼 JSON 的文章整理

利用 JSONDecoder 和 Codable 解析 JSON 和生成自訂型別資料

medium.com

從 PostMan 串接 API 的範例說明 — 設定 URL， HTTP method，header & body

開發 iOS App 時，我們時常利用 PostMan 串接 API，測試 API 功能是否正常。

medium.com

心得:

我一開始是不太知道該如何進行JSON的解析，後來把API 網址丟到Postman之後，且透過閱讀其他同學的文章以及大量的練習，還有請Ai幫忙檢查，才知道該怎麼做、問題在哪裡！

最主要的，仍是透過大量的練習，才知道問題可以怎麼被解決、該如何解、以及如何處理資料！

Country:

Website:

REST Countries

Get information about countries via a RESTful API

restcountries.com

API:

 https://restcountries.com/v3.1/all

資料解析：

Country的JSON資料結構，我一開始做覺得算是蠻複雜的，如果一開始不熟悉，蠻容易印不資料內容來，但最主要就是要分清楚括號之間的差異，最主要就是要分清楚是Int / Double / String / Date / URL。

首先，要先把API網頁貼到Postman裡面的GET欄位，並按出send，並選擇HTTPS裡面的GET method去找到資料內容。

基本上要先了解資料結構本身，才有辦法知道要如何解析完整的資料結構，在這次的練習當中，由於每個資料結構的內容都不同，所以必須要瞭解資料結構內容，才有辦法解析資料。

使用 Postman 研究 API & 產生 Swift 程式

在開始撰寫 Swift 程式串接後台的 API 前，最好先利用一些工具確認後台功能是否正常，以及檢查對方回傳的 JSON 資料格式。如果發現後台有 bug，我們 App 工程師就可以先去買個下午茶休息一下了。

medium.com

從 PostMan 串接 API 的範例說明 — 設定 URL， HTTP method，header & body

開發 iOS App 時，我們時常利用 PostMan 串接 API，測試 API 功能是否正常。

medium.com

取得資料後，再來就是要定義資料結構，首先要先認識括號差異，例如:方括弧(square brackets) 和花括弧 (curly brackets)的差異，以及冒號前後之間的內容，找到資料前後對應的關係。

可以先以一小串的資料做為練習內容:

[
    {
        "name": {
            "common": "Cyprus",
            "official": "Republic of Cyprus",
            "nativeName": {
                "ell": {
                    "official": "Δημοκρατία της Κύπρος",
                    "common": "Κύπρος"
                },
                "tur": {
                    "official": "Kıbrıs Cumhuriyeti",
                    "common": "Kıbrıs"
                }
            }
        },
        "tld": [
            ".cy"
        ],
        "cca2": "CY",
        "ccn3": "196",
        "cca3": "CYP",
        "cioc": "CYP",
        "independent": true,
        "status": "officially-assigned",
        "unMember": true,
        "currencies": {
            "EUR": {
                "name": "Euro",
                "symbol": "€"
            }
        },
        "idd": {
            "root": "+3",
            "suffixes": [
                "57"
            ]
        },
        "capital": [
            "Nicosia"
        ],
        "altSpellings": [
            "CY",
            "Kýpros",
            "Kıbrıs",
            "Republic of Cyprus",
            "Κυπριακή Δημοκρατία",
            "Kıbrıs Cumhuriyeti"
        ],
        "region": "Europe",
        "subregion": "Southern Europe",
        "languages": {
            "ell": "Greek",
            "tur": "Turkish"
        },
        "translations": {
            "ara": {
                "official": "جمهورية قبرص",
                "common": "قبرص"
            },
            "bre": {
                "official": "Republik Kiprenez",
                "common": "Kiprenez"
            },
            "ces": {
                "official": "Kyperská republika",
                "common": "Kypr"
            },
            "cym": {
                "official": "Gweriniaeth Cyprus",
                "common": "Cyprus"
            },
            "deu": {
                "official": "Republik Zypern",
                "common": "Zypern"
            },
            "est": {
                "official": "Küprose Vabariik",
                "common": "Küpros"
            },
            "fin": {
                "official": "Kyproksen tasavalta",
                "common": "Kypros"
            },
            "fra": {
                "official": "République de Chypre",
                "common": "Chypre"
            },
            "hrv": {
                "official": "Republika Cipar",
                "common": "Cipar"
            },
            "hun": {
                "official": "Ciprusi Köztársaság",
                "common": "Ciprus"
            },
            "ita": {
                "official": "Repubblica di Cipro",
                "common": "Cipro"
            },
            "jpn": {
                "official": "キプロス共和国",
                "common": "キプロス"
            },
            "kor": {
                "official": "키프로스 공화국",
                "common": "키프로스"
            },
            "nld": {
                "official": "Republiek Cyprus",
                "common": "Cyprus"
            },
            "per": {
                "official": "جمهوری قبرس",
                "common": "قِبرِس"
            },
            "pol": {
                "official": "Republika Cypryjska",
                "common": "Cypr"
            },
            "por": {
                "official": "República de Chipre",
                "common": "Chipre"
            },
            "rus": {
                "official": "Республика Кипр",
                "common": "Кипр"
            },
            "slk": {
                "official": "Cyperská republika",
                "common": "Cyprus"
            },
            "spa": {
                "official": "República de Chipre",
                "common": "Chipre"
            },
            "srp": {
                "official": "Кипарска Република",
                "common": "Кипар"
            },
            "swe": {
                "official": "Republiken Cypern",
                "common": "Cypern"
            },
            "tur": {
                "official": "Kıbrıs Cumhuriyeti",
                "common": "Kıbrıs"
            },
            "urd": {
                "official": "جمہوریہ قبرص",
                "common": "قبرص"
            },
            "zho": {
                "official": "塞浦路斯共和国",
                "common": "塞浦路斯"
            }
        },
        "latlng": [
            35.0,
            33.0
        ],
        "landlocked": false,
        "area": 9251.0,
        "demonyms": {
            "eng": {
                "f": "Cypriot",
                "m": "Cypriot"
            },
            "fra": {
                "f": "Chypriote",
                "m": "Chypriote"
            }
        },
        "flag": "🇨🇾",
        "maps": {
            "googleMaps": "https://goo.gl/maps/77hPBRdLid8yD5Bm7",
            "openStreetMaps": "https://www.openstreetmap.org/relation/307787"
        },
        "population": 1207361,
        "gini": {
            "2018": 32.7
        },
        "fifa": "CYP",
        "car": {
            "signs": [
                "CY"
            ],
            "side": "left"
        },
        "timezones": [
            "UTC+02:00"
        ],
        "continents": [
            "Europe"
        ],
        "flags": {
            "png": "https://flagcdn.com/w320/cy.png",
            "svg": "https://flagcdn.com/cy.svg",
            "alt": "The flag of Cyprus has a white field, at the center of which is a copper-colored silhouette of the Island of Cyprus above two green olive branches crossed at the stem."
        },
        "coatOfArms": {
            "png": "https://mainfacts.com/media/images/coats_of_arms/cy.png",
            "svg": "https://mainfacts.com/media/images/coats_of_arms/cy.svg"
        },
        "startOfWeek": "monday",
        "capitalInfo": {
            "latlng": [
                35.17,
                33.37
            ]
        },
        "postalCode": {
            "format": "####",
            "regex": "^(\\d{4})$"
        }
    },
    {
        "name": {
            "common": "Eritrea",
            "official": "State of Eritrea",
            "nativeName": {
                "ara": {
                    "official": "دولة إرتريا",
                    "common": "إرتريا‎"
                },
                "eng": {
                    "official": "State of Eritrea",
                    "common": "Eritrea"
                },
                "tir": {
                    "official": "ሃገረ ኤርትራ",
                    "common": "ኤርትራ"
                }
            }
        },
        "tld": [
            ".er"
        ],
        "cca2": "ER",
        "ccn3": "232",
        "cca3": "ERI",
        "cioc": "ERI",
        "independent": true,
        "status": "officially-assigned",
        "unMember": true,
        "currencies": {
            "ERN": {
                "name": "Eritrean nakfa",
                "symbol": "Nfk"
            }
        },
        "idd": {
            "root": "+2",
            "suffixes": [
                "91"
            ]
        },
        "capital": [
            "Asmara"
        ],
        "altSpellings": [
            "ER",
            "State of Eritrea",
            "ሃገረ ኤርትራ",
            "Dawlat Iritriyá",
            "ʾErtrā",
            "Iritriyā"
        ],
        "region": "Africa",
        "subregion": "Eastern Africa",
        "languages": {
            "ara": "Arabic",
            "eng": "English",
            "tir": "Tigrinya"
        },
        "translations": {
            "ara": {
                "official": "دولة إريتريا",
                "common": "إريتريا"
            },
            "bre": {
                "official": "Stad Eritrea",
                "common": "Eritrea"
            },
            "ces": {
                "official": "Stát Eritrea",
                "common": "Eritrea"
            },
            "cym": {
                "official": "Gwladwriaeth Eritrea",
                "common": "Eritrea"
            },
            "deu": {
                "official": "Staat Eritrea",
                "common": "Eritrea"
            },
            "est": {
                "official": "Eritrea Riik",
                "common": "Eritrea"
            },
            "fin": {
                "official": "Eritrean valtio",
                "common": "Eritrea"
            },
            "fra": {
                "official": "État d'Érythrée",
                "common": "Érythrée"
            },
            "hrv": {
                "official": "Država Eritreji",
                "common": "Eritreja"
            },
            "hun": {
                "official": "Eritrea",
                "common": "Eritrea"
            },
            "ita": {
                "official": "Stato di Eritrea",
                "common": "Eritrea"
            },
            "jpn": {
                "official": "エリトリア国",
                "common": "エリトリア"
            },
            "kor": {
                "official": "에리트레아국",
                "common": "에리트레아"
            },
            "nld": {
                "official": "Staat Eritrea",
                "common": "Eritrea"
            },
            "per": {
                "official": "جمهوری اریتره",
                "common": "اریتره"
            },
            "pol": {
                "official": "Państwo Erytrea",
                "common": "Erytrea"
            },
            "por": {
                "official": "Estado da Eritreia",
                "common": "Eritreia"
            },
            "rus": {
                "official": "Государство Эритрея",
                "common": "Эритрея"
            },
            "slk": {
                "official": "Eritrejský štát",
                "common": "Eritrea"
            },
            "spa": {
                "official": "Estado de Eritrea",
                "common": "Eritrea"
            },
            "srp": {
                "official": "Држава Еритреја",
                "common": "Еритреја"
            },
            "swe": {
                "official": "Staten Eritrea",
                "common": "Eritrea"
            },
            "tur": {
                "official": "Eritre Devleti",
                "common": "Eritre"
            },
            "urd": {
                "official": "ریاستِ ارتریا",
                "common": "ارتریا"
            },
            "zho": {
                "official": "厄立特里亚",
                "common": "厄立特里亚"
            }
        },
        "latlng": [
            15.0,
            39.0
        ],
        "landlocked": false,
        "borders": [
            "DJI",
            "ETH",
            "SDN"
        ],
        "area": 117600.0,
        "demonyms": {
            "eng": {
                "f": "Eritrean",
                "m": "Eritrean"
            },
            "fra": {
                "f": "Érythréenne",
                "m": "Érythréen"
            }
        },
        "flag": "🇪🇷",
        "maps": {
            "googleMaps": "https://goo.gl/maps/HRyqUpnPwwG6jY5j6",
            "openStreetMaps": "https://www.openstreetmap.org/relation/296961"
        },
        "population": 5352000,
        "fifa": "ERI",
        "car": {
            "signs": [
                "ER"
            ],
            "side": "right"
        },
        "timezones": [
            "UTC+03:00"
        ],
        "continents": [
            "Africa"
        ],
        "flags": {
            "png": "https://flagcdn.com/w320/er.png",
            "svg": "https://flagcdn.com/er.svg",
            "alt": "The flag of Eritrea comprises three triangles — a large red isosceles triangle with its base spanning the hoist end and its apex at the midpoint on the fly end, and a green and blue right-angled triangle above and beneath the red triangle. On the hoist side of the red triangle is a golden vertical olive branch encircled by a golden olive wreath."
        },
        "coatOfArms": {
            "png": "https://mainfacts.com/media/images/coats_of_arms/er.png",
            "svg": "https://mainfacts.com/media/images/coats_of_arms/er.svg"
        },
        "startOfWeek": "monday",
        "capitalInfo": {
            "latlng": [
                15.33,
                38.93
            ]
        }
    },

Structure:

import UIKit

// 定義結構體以匹配 JSON 結構
struct Country: Codable {
    let name: Name
    let tld: [String]?
    let cca2: String?
    let ccn3: String?
    let cca3: String?
    let cioc: String?
    let independent: Bool?
    let unMember: Bool?
    let currencies: [String: Currency]?
    let idd: Idd
    let capital: [String]?
    let altSpellings: [String]?
    let region: String
    let subregion: String?
    let languages: [String: String]?
    let translations: [String: Translation]?
    let latlng: [Double]?
    let landlocked: Bool
    let area: Double
    let demonyms: [String: Demonym]?
    let flag: String
    let maps: Maps
    let population: Int
    let gini: [String: Double]?
    let fifa: String?
    let car: Car
    let timezones, continents: [String]
    let flags: ImageURLs
    let coatOfArms: ImageURLs
    let startOfWeek: String
    let capitalInfo: CapitalInfo
    let postalCode: PostalCode?
}

struct Name: Codable {
    let common, official: String
    let nativeName: [String: NativeName]?
}

struct NativeName: Codable {
    let official, common: String
}

struct Currency: Codable {
    let name: String
    let symbol: String?
}

struct Idd: Codable {
    let root: String?
    let suffixes: [String]?
}

struct Translation: Codable {
    let official: String?
    let common: String?
}

struct Demonym: Codable {
    let f, m: String
}

struct Maps: Codable {
    let googleMaps: String?
    let openStreetMaps: String?
}

struct Car: Codable {
    let signs: [String]?
    let side: String
}

struct ImageURLs: Codable {
    let png: String?
    let vg: String?
}

struct CapitalInfo: Codable {
    let latlng: [Double]?
}

struct PostalCode: Codable {
    let format: String?
    let regex: String?
}

FetchData:

運用URLSession.shared.dataTask，找到這API網址的資料，並且運用do catch的寫法，處理error handling，當API資料被找到的時候，do的部分會被執行，到catch時，則印出error，最後一定要記得加上.resume()，才會開始執行任務。(細節可以參考下列彼得潘老師的文章內容)

// 解析 JSON 資料的函數
func fetchCountryData() {
    guard let url = URL(string: "https://restcountries.com/v3.1/all") else { return }
    
    URLSession.shared.dataTask(with: url) { data, response, error in
        guard let data = data else {
            print(error?.localizedDescription ?? "Unknown error")
            return
        }
        do {
            let decoder = JSONDecoder()
            let countries = try decoder.decode([Country].self, from: data)
            // 現在可以使用解析後的國家資料了
            // 例如，列印每個國家的首都和面積
            for country in countries {
                print("\(country.name.common): \(country.capital?.first ?? "No capital"), Area: \(country.area) km²")
            }
        } catch {
            print("Decoding error: \(error)")
        }
    }.resume()
}

// 呼叫函數以啟動解析過程
fetchCountryData()

URL Loading System | Apple Developer Documentation

Interact with URLs and communicate with servers using standard Internet protocols.

developer.apple.com

Fetching website data into memory | Apple Developer Documentation

Receive data directly into memory by creating a data task from a URL session.

developer.apple.com

為什麼 URLSessionTask 要呼叫 resume() 才會啟動 ?

當我們開發 iOS App，撰寫網路相關功能時，基本上可分為以下兩個步驟:

apppeterpan.medium.com

Swift從零開始-Day17: Error Handling學習 — iT 邦幫忙::一起幫忙解決難題，拯救 IT 人的一天

分類：基本知識學習在前兩天的下載圖片的程式碼中，我有用到錯誤處理的概念，但是自己對於這塊沒有太大的了解，因此獨立出來學習。 1. Guard語法基礎學習在說明Error handling時，建議須…

ithelp.ithome.com.tw

Result:

在function裡面，運用for in的方法，試著印出Country裡面的name的common內容，資料就會產生在Debugger console裡面。

加上Optional

之前有因為沒有加上冒號，而導致在Playground裡面印不出資料，所以要在定義好的資料型別後方加上冒號 Optional(例如: string > string?)，因為不確定這個API網址裡面，有沒有這筆資料。

GitHubs:

這次是拿Peter Pan文章裡面的練習內容，是保羅大大的在GitHubs粉絲的追蹤數，找到followers的id名稱 / 追蹤人數 / 名字等等資料。

API Address:

// GitHubs API
https://api.github.com/users/twostraws/followers

Postman:

把資料丟進Postman裡面，一樣使用同樣的方法用HTTP Method的GETS，並將資料產出。

Structure:

裡面有些內容很明顯就是網址內容，這時候可以直接定義成URL。

struct GitHubs: Codable {
    let login: String
    let id: Int
    let node_id: String
    let avatar_url: URL
    let gravatar_id: String
    let url: String
    let html_url: String
    let followers_url: URL
    let following_url: URL
    let gists_url: URL
    let starred_url: URL
    let subscriptions_url: URL
    let organizations_url: URL
    let repos_url: URL
    let events_url: URL
    let received_events_url: URL
    let type: String
    let site_admin: Bool
}

Fetch Data:

也是運用同樣的寫法，將資料印出！

func fetchGitHubsData () {
    guard let url = URL(string: "https://api.github.com/users/twostraws/followers") else { return }
    URLSession.shared.dataTask(with: url) { data, response, error in
        guard let data = data else {
            print(error?.localizedDescription ?? "Unknown error")
            return
        }
        do {
            let decoder = JSONDecoder()
            let followerList = try decoder.decode([GitHubs].self, from: data)
                for followerData in followerList {
                    print("The login is: \(followerData.login)")
                    print("The id is: \(followerData.id)")
                    print("The node_id is: \(followerData.node_id)")
                    print("The avatar_url is: \(followerData.avatar_url)")
                    print("The gravatar_id is: \(followerData.gravatar_id)")
                    print("The url is: \(followerData.url)")
                    print("The html_url is: \(followerData.html_url)")
                    print("The followers_url is: \(followerData.followers_url)")
                    print("The following_url is: \(followerData.following_url)")
                    print("The gists_url is: \(followerData.gists_url)")
                    print("The starred_url is: \(followerData.starred_url)")
                    print("The subscriptions_url is: \(followerData.subscriptions_url)")
                    print("The organizations_url is: \(followerData.organizations_url)")
                    print("The repos_url is: \(followerData.repos_url)")
                    print("The events_url is: \(followerData.events_url)")
                    print("The received_events_url is: \(followerData.received_events_url)")
                    print("The type is: \(followerData.type)")
                    print("The site_admin is: \(followerData.site_admin)")
                    print("")
                }
            } catch {
                print("Decoding error: \(error)")
            }
        }.resume()
    }

Result:

TRIVIA:

Trivia是個選擇題為主的API內容，主要是練習印出來的內容為何～

API Address:

 https://opentdb.com/api.php?amount=10

Postman:

Structure

import UIKit

struct Trivia: Codable {
    let response_code: Int?
    let results: [TriviaData]
}

struct TriviaData: Codable {
    let type: String
    let difficulty: String
    let category: String
    let question:String
    let correct_answer: String
    let incorrect_answers: [String]
}

Fetch Data:

func fetchData () {
    guard let url = URL(string: "https://opentdb.com/api.php?amount=10") else {
        return
    }
    URLSession.shared.dataTask(with: url) { data, responde, error in
        guard let data = data else {
            print(error?.localizedDescription ?? "Unknown error")
            return
        }
        do {
            let decoder = JSONDecoder()
            let trivia = try decoder.decode(Trivia.self, from: data)
            if let firstQuestion = trivia.results.first {
                 
                print(firstQuestion.question)
                print(firstQuestion.type)
                print(firstQuestion.difficulty)
                print(firstQuestion.category)
                print(firstQuestion.question)
                print(firstQuestion.correct_answer)
                print(firstQuestion.incorrect_answers)
                
            } else {
                print("No question found")
            }
        } catch {
            print("Decoding error: \(error)")
        }
    }.resume()
}

fetchData()

Result:

Apple Markting RSS:

這個內容是運用Apple Marketing的RSS的訂閱，產生出有關Apple Music的相關內容。

API Address:

https://rss.applemarketingtools.com/api/v2/tw/music/most-played/10/songs.json

Postman:

Structure:

import UIKit

struct Apple: Decodable {
    let feed: Feed
}

struct Feed: Decodable {
    let title: String
    let id: String
    let author: Author
    let links: [Link]?
    let copyright: String
    let country: String
    let icon: URL
    let updated: String
    let results: [Result]
}

struct Author: Decodable {
    let name: String
    let url:  URL
}

struct Link: Decodable {
    let `self`: URL
}

struct Result: Decodable {
    let artistName: String
    let id: String
    let name: String
    let releaseDate: Date
    let kind: String
    let artistId: String
    let artistUrl: URL
    let artworkUrl100: URL
    let genres: [Genre]
    let url: URL
}

struct Genre: Decodable {
    let genreId: String
    let name: String
    let url: URL
}

Fetch Data:

func fetchData () {
    guard let url = URL(string: "https://rss.applemarketingtools.com/api/v2/tw/music/most-played/10/songs.json") else { return }
    
    URLSession.shared.dataTask(with: url) { data, response, error in
        guard let data = data else {
            print(error?.localizedDescription ?? "Can't get the data")
            return
        }
        do {
            let decoder = JSONDecoder()
            decoder.keyDecodingStrategy = .convertFromSnakeCase
            
            let dateFormatter = DateFormatter()
            dateFormatter.dateFormat = "yyyy-MM-dd"
            decoder.dateDecodingStrategy = .formatted(dateFormatter)
            
            let appleData = try decoder.decode(Apple.self, from: data)
            print(appleData.feed.title)
            print(appleData.feed.id)
            print(appleData.feed.author)
            print(appleData.feed.copyright)
            print(appleData.feed.country)
            print(appleData.feed.icon)
            print(appleData.feed.results)
            
        } catch {
            print(error)
        }
    }.resume()
}

fetchData()

Result:

Random User Generator:

API Address:

 https://randomuser.me/api/

Postman:

Structure:

import UIKit

struct RandomUserData: Decodable {
    let results: [Results]
    let info: Info
}

struct Results: Decodable {
    let gender: String
    let name: Name        // 不太確定，應該是Dict
    let location: Location
    let email: String
    let login: Login
    let registered: Registered
    let phone: String
    let cell: String
    let id: Id
    let picture: Picture
    let nat: String
}

struct Name: Decodable {
    let title: String
    let first: String
    let last: String
}

struct Location: Decodable {
    let street: Street?
    let city: String
    let state: String
    let country: String
    let postcode: Int?
    let coordinates: Coordinates
    let timezone: Timezone
}

struct Street: Decodable {
    let number: Int
    let name: String
}

struct Coordinates: Decodable {
    let latitude: String
    let longitude: String
}

struct Timezone: Decodable {
    let offset: String
    let description: String
}

struct Login: Decodable {
    let uuid: String
    let username: String
    let password: String
    let salt: String
    let md5: String
    let sha1: String
    let sha256: String
}

struct Registered: Decodable{
    let date: Date
    let age: Int
}

struct Id: Decodable {
    let name: String
    let value: String?
}

struct Picture: Decodable {
    let large: URL
    let medium: URL
    let thumbnail: URL
}

struct Info: Decodable {
    let seed: String
    let results: Int
    let page: Int
    let version: String
}

Fetch Data:

func fetchRandomUserData() {
    guard let url = URL(string: "https://randomuser.me/api/") else { return }
    URLSession.shared.dataTask(with: url) { data, response, error in
        guard let data = data else {
            print(error ?? "Can't get the data" )
            return
        }
        do {
            let decoder = JSONDecoder()
            decoder.dateDecodingStrategy = .iso8601
            
            let dateFormatter = DateFormatter()
            dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZ"
            dateFormatter.locale = Locale(identifier: "en_US_POSIX")
            dateFormatter.timeZone = TimeZone(secondsFromGMT: 0)
            decoder.dateDecodingStrategy = .formatted(dateFormatter)
        
            let randomUserData = try decoder.decode(RandomUserData.self, from: data)
            print(randomUserData.info.page)
            print(randomUserData.info.seed)
            print(randomUserData.info.results)
            print(randomUserData.info.version)
            
        } catch {
            print("資料錯誤:\(error)")
        }
    }.resume()
}

fetchRandomUserData()

Result:

Joker API:

API Address:

 https://v2.jokeapi.dev/joke/Any

Postman:

Structure:

struct Joker: Decodable {
    let error: Bool
    let category: String
    let type: String
    let joke: String?
    let flags: Flags
    let id: Int
    let safe: Bool
    let lang: String
}

struct Flags: Decodable {
    let nsfw: Bool
    let religious: Bool
    let political: Bool
    let racist: Bool
    let sexist: Bool
    let explicit: Bool
}

Fetch Data:

func fetchJoke() {
    guard let url = URL(string: "https://v2.jokeapi.dev/joke/Any") else {
        print("Invalid URL")
        return
    }
    
    URLSession.shared.dataTask(with: url) { data, response, error in
        guard let data = data else {
            print(error?.localizedDescription ?? "Can't get the data")
            return
        }
        do {
            let decoder = JSONDecoder()
            decoder.keyDecodingStrategy = .convertFromSnakeCase
            let jokeData = try decoder.decode(Joker.self, from: data)
            print(jokeData.error)
            print(jokeData.id)
        } catch {
            print("Decoding error: \(error)")
        }
    }.resume()
}

fetchJoke()

Result:

iTunes:

API Address:

 https://itunes.apple.com/search?term=jack+johnson&limit=25

Postman:

Structure:

import UIKit

struct Itunes: Decodable {
    let resultCount: Int
    let results: [Results]
}

struct Results: Decodable {
    let wrapperType: String
    let kind: String
    let artistName: String
    let collectionName: String
    let trackName: String
    let collectionCensoredName: String
    let trackCensoredName: String
    let collectionArtistId: Int
    let collectionArtistViewUrl: URL
    let collectionViewUrl: URL
    let trackViewUrl: URL
    let previewUrl: URL
    let artworkUrl30: URL
    let artworkUrl60: URL
    let collectionPrice: Double
    let trackPrice: Double
    let trackRentalPrice: Double
    let collectionHdPrice: Double
    let trackHdPrice: Double
    let trackHdRentalPrice: Double
    let releaseDate: Date
    let collectionExplicitness: String
    let trackExplicitness: String
    let discCount: Int
    let discNumber: Int
    let trackCount: Int
    let trackNumber: Int
    let trackTimeMillis: Int
    let country: String
    let currency: String
    let primaryGenreName: String
    let contentAdvisoryRating: String
    let shortDescription: String
    let longDescription: String
    let hasITunesExtras: Bool
}

Fetch Data:


func fetchData () {
    let urlString = "https://itunes.apple.com/search?term=jack+johnson&limit=25"
    guard let url = URL(string: urlString) else {
        print("Invalid URL")
        return
    }

    let task = URLSession.shared.dataTask(with: url) { data, response, error in
        if let error = error {
            print("Error fetching data: \(error.localizedDescription)")
            return
        }
        
        guard let data = data else {
            print("No data returned from URL")
            return
        }

        do {
            let decoder = JSONDecoder()
            decoder.dateDecodingStrategy = .iso8601
            let itunesData = try decoder.decode(Itunes.self, from: data)
            print("Result Count: \(itunesData.resultCount)")
            if let firstResult = itunesData.results.first {
                print("First Result Name: \(firstResult.trackName)")
            }
        } catch {
            print("Error decoding JSON: \(error)")
        }
    }
    task.resume()
}


fetchData()

Result:

YouBike API:

這個是在台北市資料開放平臺的資料，可以找到政府所公開的資料，例如:垃圾車的到站時間、Youbike等等，有興趣可以這網站看看！

臺北市資料大平臺

臺北市政府為推動開放政府（Open Government）之資料開放政策，整合臺北市政府各機關開放資料於單一入口網站，供民眾瀏覽及程式開發者加值應用。

data.taipei

API Address:

 https://tcgbusfs.blob.core.windows.net/dotapp/youbike/v2/youbike_immediate.json

Postman:

Structure:

struct YouBikeData: Decodable {
    let sno: String
    let sna: String
    let tot: Int
    let sbi: Int
    let sarea: String
    let mday: String
    let lat: Double
    let lng: Double
    let ar: String
    let sareaen: String
    let aren: String
    let bemp: Int
    let act: String
    let srcUpdateTime: String
    let updateTime: String
    let infoTime: String
    let infoDate: String
}

Fetch Data:

func fetchData () {
    guard let url = URL(string: " https://tcgbusfs.blob.core.windows.net/dotapp/youbike/v2/youbike_immediate.json") else {
        return
    }
    let task = URLSession.shared.dataTask(with: url) { data, response, error in
        guard let data = data, error == nil  else {
            print(error?.localizedDescription ?? "Can't get the data")
            return
        }
        do {
            let decoder = JSONDecoder()
            decoder.keyDecodingStrategy = .convertFromSnakeCase
            let youbikeDataset = try decoder.decode([YouBikeData].self, from: data)
            
            if let firstStation = youbikeDataset.first {
                print("DEBUG PRINT: Youbike資料:\(firstStation.bemp)")
                print("DEBUG PRINT: 所有的Youbike區域:\(firstStation.sareaen)")
                print("DEBUG PRINT: 目前Youbike的車位總數資料\(firstStation.tot)")
            }
        } catch {
            print(error)
        }
    }
    task.resume()
}

fetchData()

Result:

📝 筆記:

在這次練習除了瞭解到如何運用Decode做資料分析、還有認識新的程式寫法，Error handling / do catch的用法 / Closure等等，認識網路這塊之後，才知道說如何透過程式抓到資料，覺得實在有趣！

Codable / Decodable / Encodable:

此外，我後來想知道Codable & Decodable & Encodable之間的差異，講白話一點，Decodable就是解碼、Encodable就是編碼，而Codable就是這兩個protocol的集合，兩者都是專門處理JSON的方法！

我個人認為在Stackoverflow上的解釋還蠻好懂的，可以作為參考 :)

Swift Encodable, Decodable Vs Codable

Found in Apple doc, that Codable protocol is composed of Encodable and Decodable. Thus, Codable = Encodable &amp…

stackoverflow.com

Swift — 說說 Codable （ Decodable & Encodable）

利用 Swift 中的 Codable 協議來方便編／解碼資料。

jjeremy-xue.medium.com

Dicitonary or Array?

當資料外圍是中括號 [] 的在解析型別時需加上 [] 標註為 Array，資料外圍是花括號 {} 則是 Dictionary，型別上不需特別備註。

下列為Apple Marketing RSS的練習一小部分，就是看出Genre為部分的解析內容，而到了Result的時候，就變成一個Array，這時候就要回頭看一下JSON裡面的內容為何。

struct Result: Decodable {
    let artistName: String
    let id: String
    let name: String
    let releaseDate: Date
    let kind: String
    let artistId: String
    let artistUrl: URL
    let artworkUrl100: URL
    let genres: [Genre]
    let url: URL
}

struct Genre: Decodable {
    let genreId: String
    let name: String
    let url: URL
}

當時在練習Country API的時候，就有很多貌似Array，但實際上是dictionary，所以一定要看清楚！

型別定義:

如果是整個 JSON 資料皆被中括號 [ ] 框住( Array)，則在進行 decode 動作時，記得框住整筆資料(可以參考youbike的例子):

let youbikeDataset = try decoder.decode([YouBikeData].self, from: data)

型別設置有誤。

Double/String 的話很有可能是沒有解碼到日期格式，這時候要確定是否有無設置decoder.dateDecodingStrategy。

相同型別在struct裡面的兩種寫法:

後面在練習的時候，有發現到，如果是相同屬性的資料結構，我們可以運用命名的後面加上逗號，以減少寫code的數量，前提是命名的內容都要是可以被找到的內容，不然其實仍是要拆開來寫的。

舉例:

一般寫法:

struct NativeName: Codable {
    let official: String
    let common: String
}

簡潔:

struct NativeName: Codable {
    let official, common: String
}

My GitHubs:

GitHub - dwhao84/HW-45-JSON-Decoder

Contribute to dwhao84/HW-45-JSON-Decoder development by creating an account on GitHub.

github.com

HW#45 JSON Decoder

練習主題:

新手的 Swift JSON decode 練習題

搭配 AI 建立自己感興趣的 JSON API

使用 Postman 研究 API & 產生 Swift 程式

在開始撰寫 Swift 程式串接後台的 API 前，最好先利用一些工具確認後台功能是否正常，以及檢查對方回傳的 JSON 資料格式。如果發現後台有 bug，我們 App 工程師就可以先去買個下午茶休息一下了。

iOS 解碼 & 編碼 JSON 的文章整理

利用 JSONDecoder 和 Codable 解析 JSON 和生成自訂型別資料

從 PostMan 串接 API 的範例說明 — 設定 URL， HTTP method，header & body

開發 iOS App 時，我們時常利用 PostMan 串接 API，測試 API 功能是否正常。

心得:

Country:

REST Countries

Get information about countries via a RESTful API

使用 Postman 研究 API & 產生 Swift 程式

在開始撰寫 Swift 程式串接後台的 API 前，最好先利用一些工具確認後台功能是否正常，以及檢查對方回傳的 JSON 資料格式。如果發現後台有 bug，我們 App 工程師就可以先去買個下午茶休息一下了。

從 PostMan 串接 API 的範例說明 — 設定 URL， HTTP method，header & body

開發 iOS App 時，我們時常利用 PostMan 串接 API，測試 API 功能是否正常。

URL Loading System | Apple Developer Documentation

Interact with URLs and communicate with servers using standard Internet protocols.

Fetching website data into memory | Apple Developer Documentation

Receive data directly into memory by creating a data task from a URL session.

為什麼 URLSessionTask 要呼叫 resume() 才會啟動 ?

當我們開發 iOS App，撰寫網路相關功能時，基本上可分為以下兩個步驟:

Swift從零開始-Day17: Error Handling學習 — iT 邦幫忙::一起幫忙解決難題，拯救 IT 人的一天

分類：基本知識學習 在前兩天的下載圖片的程式碼中，我有用到錯誤處理的概念，但是自己對於這塊沒有太大的了解，因此獨立出來學習。 1. Guard語法基礎學習 在說明Error handling時，建議須…

GitHubs:

TRIVIA:

Apple Markting RSS:

Random User Generator:

Joker API:

iTunes:

YouBike API:

臺北市資料大平臺

臺北市政府為推動開放政府（Open Government）之資料開放政策，整合臺北市政府各機關開放資料於單一入口網站，供民眾瀏覽及程式開發者加值應用。

📝 筆記:

Swift Encodable, Decodable Vs Codable

Found in Apple doc, that Codable protocol is composed of Encodable and Decodable. Thus, Codable = Encodable &amp…

Swift — 說說 Codable （ Decodable & Encodable）

利用 Swift 中的 Codable 協議來方便編／解碼資料。

GitHub - dwhao84/HW-45-JSON-Decoder

Contribute to dwhao84/HW-45-JSON-Decoder development by creating an account on GitHub.

Written by  Dawei

分類：基本知識學習在前兩天的下載圖片的程式碼中，我有用到錯誤處理的概念，但是自己對於這塊沒有太大的了解，因此獨立出來學習。 1. Guard語法基礎學習在說明Error handling時，建議須…