在 Swift 中初始化字典的不同方法? [英] Different ways to initialize a dictionary in Swift?

问题描述

据我所知，在 Swift 中有 4 种方法可以声明字典:

As far as I know, there are 4 ways to declare a dictionary in Swift:

var dict1: Dictionary<String, Double> = [:]
var dict2 = Dictionary<String, Double>()
var dict3: [String:Double] = [:]
var dict4 = [String:Double]()

这四个选项似乎产生了相同的结果.

It seems these four options yields the same result.

这两者有什么区别?

推荐答案

您所做的只是注意到您可以:

All you're doing is noticing that you can:

• 使用显式的变量类型，或者让 Swift 根据分配给它的值来推断变量的类型.

• Use explicit variable typing, or let Swift infer the type of the variable based on the value assigned to it.

使用正式指定的泛型结构符号Dictionary，或者使用内置的语法糖"来描述字典类型[String:Double].

Use the formal specified generic struct notation Dictionary<String,Double>, or use the built-in "syntactic sugar" for describing a dictionary type [String:Double].

二乘以二等于四.

然后实际上您忽略了一些可能性；例如，你可以说

And then there are in fact some possibilities you've omitted; for example, you could say

var dict5 : [String:Double] = [String:Double]()

当然，在现实生活中，您可能没有做这些事情，而只需将实际字典分配给您的变量:

And of course in real life you are liable to do none of these things, but just assign an actual dictionary to your variable:

var dict6 = ["howdy":1.0]

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