Swift中的for循环基本使用

//第一种
let a = 100;
for i in 0 ..< a {
print("a=\(i)");
}

//第二种 for循环不需要i的写法
let a = 100;
for _ in 0..<a {
print("a=\(a)");
}

数组的使用

定义一个不可变数

let array : Array<String> = ["lxd", "xiaoming", "xiaohong", "xiaogang"]
或者

let array1 : [String] = ["lxd", "xiaoming", "xiaohong", "xiaogang"]```
let array2 = ["lxd", "xiaoming", "xiaohong", "xiaogang"]
let array3 : [Int] = [10, 20, 30]
let array4 : Array<Any> = ["lxd", "cc", 9.99]
let array5 : [Any] = [18, "why", 1.88]
let array6 = [18, "why", 1.88] as [Any]
定义可变数组

var names : [String] = ["lxd", "xiaoming", "xiaohong", "xiaogang"]
定义一个空数组

var names3 = String
或者
var names1 : [String] = Array()
var names2 = Array<String>()
可变数组
添加元素

names.append("xiaokai")
names.insert("lxd", at: 2)
删除数组

names.removeAll()
names.remove(at: 0)
修改元素

names[0] = "dd"
取出某个元素

names[2]
names.firstIndex(of: "xiaoming")
names.lastIndex(of: "xiaohong")
遍历数组

for i in 0..<names.count {
print(names[i])
}
for item in names {
print(item)
}
指定区间遍历

for i in 0..<2 {
print(names[i])
}

for item in names[0..<2] {
print(item)
}
数组合并

//两个数组中存放的元素类型一致
let name4 = ["qq", "ww"]
var name5 = ["ee", "rr"]
let name6 = name4 + name5

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