Real World Example: Fetch JSON using NSURLSession and populate a UITableView Part 1.

In past posts I’ve covered topics such as functions, loops, dictionaries, string interpolation, conditional statements and also switch cases.

In this post I will try to use many of the topics I’ve covered by creating a very barebones iOS application that fetches some JSON from a web API, then we will use this data to populate a simple UITableView.

While building this app we will be utilizing:

• Functions
• Arrays
• Dictionaries
• NSURLSession
• UITableViewController

Let’s get started.

First we need some JSON with a url to access it.

While preparing for this post, I wrote some super simple JSON and stored it at myjson.com.

You can use mine here: https://api.myjson.com/bins/vi56v.

Visit the link, you’ll see simple JSON where there’s an array(list) of companies.

Open Xcode

Let’s open Xcode and create a single view application.

Navigate to ViewController.swift.

Your default ViewController.swift should look like this:

Let’s start writing some code.

Start by creating a function called parseJSON() after viewDidLoad().

This is where we are going to have our network logic to grab our JSON from the web API.

Let’s define our url:

We are using let instead of var because we won’t be manipulating this url.

Now let’s add NSURLSession:

Inside this task block is where we will check for errors and put our data into an array to populate our table.

Let’s check for any errors & if theres any empty data:

I’ll explain why we aren’t using if else statements later in another post.

Update: I wrote a post on guards. Check it out.

Now we need to convert our JSON to NSDictionary with JSON Serialization.

Now what we have a NSDictionary, we can tap into “companies” key and put all the values into an NSMutableArray.

We then would loop into this array and add each value to a local defined array.

Let’s define our local array.

Now that we have a local array defined we can move onto putting our “companies” into our tableArray.

We need to add task.resume() outside our task block.

Should look like so:

Now call parseJSON() in viewDidLoad and you should see the array in the console.

Stay tuned…

I remember when I was learning to program for iOS, super long articles would be pretty frustrating and hard to follow so that’s why I am breaking this topic up into two parts.

So stay tuned for part 2 of this post where I’ll cover how to use the tableArray to populate a UITableView 👍 .