Swift：声明一个空字典 [英] Swift: declare an empty dictionary

问题描述

我开始学习 swift ，遵循苹果提供的Swift的iBook - Swift编程语言。该书说要创建一个空字典，应该使用 [：] 与将声明数组 [] 相同： / p>

我宣布一个空数组如下：

  let emptyArr = [ ] //或String []（）
  

但是在声明空字典时，我会收到语法错误： / p>

  let emptyDict = [：] 
  

如何申报一个空字典？

解决方案

  var emptyDictionary = [String：String]（）
  

­

  var populatedDictionary = [key1：value1，key2：value2] 
  

注意：如果要随着时间更改字典的内容，请将其声明为 var （变量）。您可以将一个空字典声明为 let （常量），但如果您有意图随时间更改其内容，则无意义，因为常数初始化后不能更改。

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旧答案：

创建类型为< String，String> 的空字典如下所示：

  var emptyDictionary = Dictionary< String，String>（）
  

I am beginning to learn swift by following the iBook-The Swift Programming Language on Swift provided by Apple. The book says to create an empty dictionary one should use [:] same as while declaring array as []:

I declared an empty array as follows :

let emptyArr = [] // or String[]()

But on declaring empty dictionary, I get syntax error:

let emptyDict = [:]

How do I declare an empty dictionary?

解决方案

var emptyDictionary = [String: String]()

­

var populatedDictionary = ["key1": "value1", "key2": "value2"]

Note: if you are going to change the contents of the dictionary over time then declare it as a var (variable). You can declare an empty dictionary as a let (constant) but it is pointless if you have the intention of changing its contents over time, since constant can't be changed after it has been initialized.

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Old answer:

Creating an empty dictionary of type <String, String> would look as follows:

var emptyDictionary = Dictionary<String, String>()

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