Subscripts 程式範例 — Apple’s The Swift Programming Language
Sep 9, 2018 · 2 min read
Subscript Syntax
subscript(index: Int) -> Int { get { // return an appropriate subscript value here } set(newValue) { // perform a suitable setting action here }}
乘法範例
struct TimesTable { let multiplier: Int subscript(index: Int) -> Int { return multiplier * index }}let threeTimesTable = TimesTable(multiplier: 3)print("six times three is \(threeTimesTable[6])")// Prints "six times three is 18"
Subscript Usage
var numberOfLegs = ["spider": 8, "ant": 6, "cat": 4]numberOfLegs["bird"] = 2
Subscript Options
subscript 可以有多個參數
例子: 矩陣
struct Matrix { let rows: Int, columns: Int var grid: [Double] init(rows: Int, columns: Int) { self.rows = rows self.columns = columns grid = Array(repeating: 0.0, count: rows * columns) } func indexIsValid(row: Int, column: Int) -> Bool { return row >= 0 && row < rows && column >= 0 && column < columns } subscript(row: Int, column: Int) -> Double { get { assert(indexIsValid(row: row, column: column), "Index out of range") return grid[(row * columns) + column] } set { assert(indexIsValid(row: row, column: column), "Index out of range") grid[(row * columns) + column] = newValue } }}var matrix = Matrix(rows: 2, columns: 2)matrix[0, 1] = 1.5matrix[1, 0] = 3.2

