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

©xgqfrms 2012-2020

www.cnblogs.com/xgqfrms 发布文章使用：只允许注册用户才可以访问！

原创文章，版权所有©️xgqfrms, 禁止转载

标签：Function,return,level,Int,argument,colors,num,func,Swift
来源： https://www.cnblogs.com/xgqfrms/p/16256322.html