Swift学习笔记

变量与常量

变量

var name :String 
//定义变量类型
name = "cry"    
//给变量赋值cry
var b:String
var xx = "my name is"
var a:String = "my name is" + name
b = "\(xx)\(name)"
print(a)
print(b)

常量

let c :String = "my name is cry" 
//定义常量并赋值,而且c的值不能更改
print(c)

值类型与引用类型

值类型

struct people {
    var name: String
    var age: Int
}


var cry = people(name: "chan", age: 21)
var cry1 =  cry

cry.name = "chen"

print(cry.name,cry.age)
print(cry1.name,cry1.age)

引用类型

class imcry  {
    var name:String = "cry"
    var age:Int = 21
}


var me = imcry()
var me2 = me

me.name = "i am cry"
print(me.name,me2.name)

数组与字典

数组

var arr = [1, 2,  3, 4]
//定义arr数组
arr.append(5)  
//末尾添加元素
arr[0] = 11 
//改变第一个数字
arr.insert(8, atIndex: 5)
arr.insert(7, atIndex: 5)
arr.insert(1, atIndex: 0)
arr.insert(6, atIndex: 5)
//数组中特定位置插入元素
//insert(n, m) 在第n个后面加上m
arr.removeAtIndex(3)
//删除特定元素
arr.removeFirst()
//删除第一个
arr.removeLast()
//删除最后一个
print(arr)
arr.removeFirst(3)
//删除最前三个
print(arr)
var arr1 : Array<Int> = [8,9,10]
//var arr1 = [8,9,10]
//var arr1 : [Int] = [7,8,9]
//给数组赋值的几种写法
var arr2 : [Int] = []
//给arr2赋空数组
arr = arr + arr1 + arr2
//将arr,arr1,arr1拼起来赋值给arr
print(arr)
print(arr2)

字典

var dict1 : [Int:Int] = [Int:Int]()//1
var dict2 = ["k1":1,"k2":2]//2
var dict3 : [Int:Int]//3
dict3 = [12:12,22:22]
var dict4 = [Int:Int]()//4
//字典的多种写法
print(dict1)
print(dict1.count)
//计算字典中key的个数
print(dict2)