标准数组，设置，字典变量创建方式Swift编程语言

Question

我是Swift语言的初学者。有许多方法可以在其中声明/创建变量。请填写下面的代码。我想知道我可以声明数组，集合和字典的所有方法。

var arr1 : [Int] 
var arr2 = [Int]() 
var arr3 : Array<Int> 
var arr4 = [1,2,3,4] 
var arr5 : Array = [1,2,3,4] 
var arr6 : [Array<Int>] 

var dict1 : [Int:Int] 
var dict2 = [Int:Int]() 
var dict3 : Dictionary<Int,Int> 
var dict4 = [1 : 2,3 : 4] 
var dict5 : Dictionary = [1 : 2,3 : 4] 
var dict6 : [Dictionary<String, Int>] 
var dict7 = [Dictionary<String, Int>]() 
var dict8 = Dictionary<Int,Int>() 

var set1 : Set<Int> 
var set2 = Set<Int>() 
var set3 : Set = [1,2,3] 
var set4 : [Set<Int>] 
var set5 = [Set<Int>]() 

Answer 1

您的列表包含形式声明以及声明和初始化后的可变

两个替代形式的阵列和字典

var arr7 : [Int] = [] // same as arr2 

var dict9 : [Int:Int] = [:] // same as dict2, dict8 

Answer 2

很多这些都不是有效的，甚至：

var arr1 : [Int] //an undefined var of type Int array, see note #1 
var arr2 = [Int]() //an array of type Int with no elements 
var arr3 : Array<Int> //same as arr1 
var arr4 = [1,2,3,4] //an array of 4 Ints 
var arr5 : Array = [1,2,3,4] //an array of 4 Ints with a redundant type annotation 
var arr6 : [Array<Int>] //an array of arrays of Ints 

var dict1 : [Int:Int] //an undefined var of type Dictionary (mapping Int keys to Int keys), see note #1 
var dict2 = [Int:Int]() //an empty dictionary mapping Int keys to Int values 
var dict3 : Dictionary<Int,Int> //same as dict1 
var dict4 = [1 : 2, 3 : 4] //a dictionary with two Int : Int mappings 
var dict5 : Dictionary = [1 : 2,3 : 4]//a dictionary with two Int mappings and a redundant type annotation 
var dict6 : [Dictionary<String, Int>] //an undefined var of type array of Dictionaries from String keys to Int values. 
var dict7 = [Dictionary<String, Int>]() //an empty array of dictionaries mapping String keys to Int values 
var dict3 : Dictionary<Int,Int> //dict 3 repeated from above? 
var dict8 = Dictionary<Int,Int>() //an empty dictionary mapping Int keys to Int values 

var set1 : Set<Int> //an undefined var of type Set (of Int), see note #1 
var set2 = Set<Int>() //an empty set of Int 
var set3 : Set = [1,2,3] //a set of 3 Ints 
var set4 : [Set<Int>] //an undefined var of type Array (of Sets of Ints), see note #1 
var set5 = [Set<Int>]() //an empty array of Sets of Ints 

注

1. 这些变量有类型注释，但没有初始化。他们不能从直到一个有效的值分配给它们

这说明[]符号的一个根本性的误解（阵列，字典和集合），然后键入注释读取。我强烈建议你阅读语言指南。