Swift学习笔记（02）——Array（数组）

Swift 数组使用有序列表存储 同一类型 的多个值，这点相对于Objective-C是有所不同的，OC中同一个数组，可以存放不同类型的元素。Swift 数组会强制检测元素的类型，如果类型不同则会报错。

数组初始化

创建空数组

//下面4种方式创建的空数组是等价的
var emptyArray : [Int] = []
var emptyArray : Array<Int> = []
var emptyArray = [Int]()
var emptyArray = Array<Int>()

创建有默认值的数组
下面的两个例子各创建了一个类型为Int，数量为5，初始值为0的数组

var allZeros = Array<Int>(repeating: 0, count: 5)  //[0, 0, 0, 0, 0]

var allZeros = [Int](repeating: 0, count: 5)  //[0, 0, 0, 0, 0]

创建一个含有4个元素的Int类型的数组

var numbers:[Int] = [0, 2, 4, 5]
//[Int]可以省去，系统能够检测出数组的类型
var numbers = [0, 2, 4, 5]

数组的增删改查

var letters = ["D", "B", "E", "A", "P", "F"]  //如果是let，则不可修改

//获取长度
letters.count  //6

//判空
letters.isEmpty  //false

//元素获取
var str: String = letters[2]  //"E"
letters.first  //返回值为可选型String?
letters.last  //同上

//最大值&最小值
letters.max()  //"P"
letters.min()  //"A"

//范围
letters[1..<3]  //["B", "E"]

//包含关系
letters.contains("A")  //true
letters.contains("M")  //false

//获取索引
letters.index(of: "P")  //4 类型为Int?
letters.index(after: 2)  //3

//遍历
for index in 0..<letters.count {
    print(letters[index])
}
for str in letters.count {
    print(str)
}
for (index, letter) in letters.enumerated() {
    print("\(index+1): \(letter)")
}

//添加元素
letters.append("C")  //["D", "B", "E", "A", "P", "F", "C"]
letters += ["O"]  //["D", "B", "E", "A", "P", "F", "C", "O"]
letters = letters + ["N"]  //["D", "B", "E", "A", "P", "F", "C", "O", "N"]
//在指定索引处添加
letters.insert("S", at: 2) //["D", "B", "S", "E", "A", "P", "F", "C", "O", "N"]

//删除元素
animals.removeFirst()  //["B", "S", "E", "A", "P", "F", "C", "O", "N"]
animals.removeLast()  //["B", "S", "E", "A", "P", "F", "C", "O"]
animals.remove(at: 2)  //["B", "S", "A", "P", "F", "C", "O"] 
animals.removeSubrange(0..<2)  //["A", "P", "F", "C", "O"]
animals.removeAll()  //[]

修改元素
var animals = ["Dog", "Pig", "Elephant", "Cat"]
animals[0] = "Fish"  //["Fish", "Pig", "Elephant", "Cat"]
animals[1...3] = ["Lion"] //["Fish", "Lion"]

二维数组

二维数组的定义

var board = [ [1024,16,2,0] , [256,4,2,0] , [64,2,0,0] , [2,0,0,0] ]
var board:[[Int]] = [ [1024,16,2,0] , [256,4,2,0] , [64,2,0,0] , [2,0,0,0] ]
var board:[Array<Int>] = = [ [1024,16,2,0] , [256,4,2,0] , [64,2,0,0] , [2,0,0,0] ]
var board:Array<[Int]> = [ [1024,16,2,0] , [256,4,2,0] , [64,2,0,0] , [2,0,0,0] ]
var board:Array<Array<Int>> = [ [1024,16,2,0] , [256,4,2,0] , [64,2,0,0] , [2,0,0,0] ]

元素获取

board[0]  //[1024,16,2,0]
board[0][0]  //1024

两个维度的信息

board.count  //4
board[0].count  //4

二维数组每个维度的元素数量可以不等

board[1].append(4)  //[[1024, 16, 2, 0], [256, 4, 2, 0, 4], [64, 2, 0, 0], [2, 0, 0, 0]]
board.append([1,2,3,4])  //[[1024, 16, 2, 0], [256, 4, 2, 0, 4], [64, 2, 0, 0], [2, 0, 0, 0], [1, 2, 3, 4]]