快速使用逗号 [英] Comma usage in swift

问题描述

  @IBAction函数func selectedGame（segue：UIStoryboardSegue）{
如果让gamePickerViewController = segue.sourceViewController为？ GamePickerViewController，
 selectedGame = gamePickerViewController.selectedGame {
 detailLabel.text = selectedGame 
 game = selectedGame 
} 
} 
  

大家好，我正在按照一个教程来学习有关swift的知识。昨天我找到了代码的这一部分，但是我找不到找到理解逗号含义的方法。您能解释一下吗？

解决方案

逗号用于将多个可选绑定组合到一个语句中，以避免不必要的嵌套。

p>

从Swift 1.2开始，if let构造现在可以立即打开多个可选对象，并包括中间的布尔条件。这样一来，您就可以表达条件控制流而不必进行不必要的嵌套。更多详细信息

例如：

  var foo：Int！ 
 var bar：字符串！ 
 
 // Swift 1.2 
 
 if let foo = foo，bar = bar {
 // foo&酒吧有价值观。 
} else {
 
} 
 
 //在Swift 1.2之前
 
如果让foo = foo {
 //嵌套如果让bar = bar {
 // foo&酒吧有价值。 
} 
} 
  

Xcode6.3及更高版本支持Swift1.2。 / p>

@IBAction func selectedGame(segue:UIStoryboardSegue) {
  if let gamePickerViewController = segue.sourceViewController as? GamePickerViewController,
    selectedGame = gamePickerViewController.selectedGame {
    detailLabel.text = selectedGame
    game = selectedGame
  }
}

Hi all, i'm following a tutorial to learn something about swift. Yesterday I found this part of code but I can not find a way to understand what it means thatcomma means. Can u pls explain me?

解决方案

The comma is used to combine multiple optional bindings into one statement to avoid unnecessary nesting.

From Swift 1.2,The if let construct can now unwrap multiple optionals at once, as well as include intervening boolean conditions. This lets you express conditional control flow without unnecessary nesting.More details

For example:

var foo: Int!
var bar: String!

// Swift 1.2

if let foo = foo,bar = bar {
    // foo & bar have values.
} else {

}

// before Swift 1.2

if let foo = foo {
    // nesting
    if let bar = bar {
        // foo & bar have value.
    }
}

Xcode6.3 and above support Swift1.2.

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