Swift Function argument All In One

- 外部参数

a single unnamed parameter

https://docs.swift.org/swift-book/LanguageGuide/Functions.html#ID160

Swift Methods argument All In One

https://docs.swift.org/swift-book/LanguageGuide/Methods.html

Methods are functions that are associated with a particular type.

方法是与特定类型相关联的函数。

function arguments / methods arguments

import Foundation // import SwiftUI // error: no such module 'SwiftUI' // print(Hello World)  // _ 外部参数名称，可以省略不写 ✅ func test(_ num: Int) -> Int {    print(num);    return num; } test(333); // test(num: 333); // extraneous 无关的 // ❌ error: extraneous argument label 'num:' in call  // 默认外部参数名称与内部参数一致，不可以省略不写 ✅ func test2(num: Int) -> Int {    print(num);    return num; } test2(num: 666); // test2(666); // ❌ error: missing argument label 'num:' in call  // 指定外部参数名称，不可以省略不写 ✅ func test3(int num: Int) -> Int {    print(num);    return num; } test3(int: 999); // test3(num: 999); // ❌ error: incorrect argument label in call (have 'num:', expected 'int:')   

import Foundation  func test(_ num: Int) -> Int {    print(num = \(num));    // num = 333    print(num);    return num; } test(333);  

errors

Global 'var' declaration requires an initializer expression or an explicitly stated getter

Unnamed parameters must be written with the empty name '_'

    // function     // 命名参数     func getColors(colors: [Color]) -> LinearGradient {       return LinearGradient(gradient: Gradient(colors: colors), startPoint: .leading, endPoint: .trailing)     }      // 未命名参数 ✅，_ 开头     func getColors2(_ colors: [Color]) -> LinearGradient {       return LinearGradient(gradient: Gradient(colors: colors), startPoint: .leading, endPoint: .trailing)       // '_' can only appear in a pattern or on the left side of an assignment       // Unnamed parameters must be written with the empty name '_'     } 

  // 命名参数，必须要写参数名称 `colors:`        .background(getColors(colors: card.gradientColors))  // 未命名参数，不需要写参数名称 ✅ .background(getColors2(card.gradientColors))  

docs

struct LevelTracker {     static var highestUnlockedLevel = 1     var currentLevel = 1      static func unlock(_ level: Int) {         if level > highestUnlockedLevel { highestUnlockedLevel = level }     }      static func isUnlocked(_ level: Int) -> Bool {         return level <= highestUnlockedLevel     }      @discardableResult     mutating func advance(to level: Int) -> Bool {         if LevelTracker.isUnlocked(level) {             currentLevel = level             return true         } else {             return false         }     } } 

https://docs.swift.org/swift-book/LanguageGuide/Methods.html

refs

http://online.swiftplayground.run/

https://www.cnblogs.com/xgqfrms/p/16255693.html

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