Swift基础使用方法（Swift开发之中的一个）

地址：https://itunes.apple.com/cn/book/swift-programming-language/id881256329?mt=11


以下我先说下主要的一些东西，大家都是刚看，所以我也难免会出现理解错误的地方。欢迎指出。当然你也能够直接看官方的文档。


一、let，var基本类型

let：常量，不能二次赋值。赋值时能够不须要指定类型，编译器依据赋值自己主动推断。也能够手工指明类型。

var：变量

let a = 12 // 申明a为常量12，类型Int
let b: Double = 12 // 申明a为常量12，手工指定类型Double

let str = "Hello, playground. "
let name = "Tom "
let count = 10
let say = str + name + String(count)  // "Hello, playground. Tom 10"

let a = 1
let b = 2
let say = "the number is \(a + b)"  // "the number is 3"

var arr = ["catfish", "water", "tulips", "blue paint"]
arr[1] = "bottle of water" // 改动第二项
arr // ["catfish", "bottle of water", "tulips", "blue paint"]

var man = [
    "like": "apple",
    "name": "Tom",
]
man["iphone"] = "5s"  // 添加字段
man["like"] = "mac"  // 改动字段
man // ["iphone": "5s", "like": "mac", "name": "Tom"]

四、控制语句

let a = 12
if a > 0 {
    // do something
} else {
   // do something
}

for i in 0..3 {
   // i = 0, 1, 2
}


for var i = 0; i < 3; ++i {
    // i = 0, 1, 2
}


// 数组
let scores = [1, 2, 3, 4, 5]
for score in scores {
    // score 
}


// 字典
let numsDic = [
    "a": [2, 3, 5, 7, 11, 13],
    "b": [1, 1, 2, 3, 5, 8],
    "c": [1, 4, 9, 16, 25],
]
for (key, numbers) in numsDic {
    for number in numbers {
        // number
    }
}

var n = 2
while n < 100 {
    n = n * 2
}


var m = 2
do {
    m = m * 2
} while m < 100