swift基础语法(一)
swift基础语法二主要讲数据类型
1.字符串
1.在swift中String是一个结构体,性能更高
String的定义.png
2.字符串的定义
var str1 = "zifuchuan" //字符串变量
let str1 = "字符串" //字符串常量
3.字符的定义
var char1 : Character = "z"//字符变量
let char1 : Character = "z" //字符常量
2.String直接支持遍历
var str2 = "hello world"
for s in str.characters{
print(s)
}
3.支持String和NSString的无缝转换
let strin = "string"
//String转换为NSString
var st = strin as NSString
//NSString转String
var str12 = st as String
let strin = "string"
let st4 = "\(st3)\(strin)"
let st5 = st3 + strin
4.字符串的拼接
格式:\(变量或常量的名字)
let age12 = 18
let height = 1.88
let st3 = "age is \(age),heigth is \(height)"
5.字符串格式化
//2:3 -> 02:03
let min = 2
let second = 3
let time = String(format: "%02d:%02d",arguments:[min,second])
6.字符串截取
//3.字符串截取
let urlString = "www.baidu.com"
//提示:不要使用string方法,因为index创建不好创建
//urlString.substringToIndex(<#T##index: Index##Index#>)
//String转nsstring,只需要在string后面加上as nsstring
let prefixStrinf = (urlString as NSString).substringToIndex(3)
//中间
let middel = (urlString as NSString).substringWithRange(NSRange(location: 4, length: 3))
//末尾
let subFixString = (urlString as NSString).substringFromIndex(8)
7.字符串进行补充
//字符串
var str: String = "hello"
let str2 = String("hello")
str.isEmpty //判断字符串是否为空
let mark = "!!!"
str + mark //str 和mark都没发生改变
str += mark
let name = "liu"
let age3 = 16
let s = "my name is \(name), age is \(age3)"
let s2 = "\\\""//输出\\
let s4 = "\""//输出"
//字符串的遍历
for c in str.characters{
print(c)
}
//mark2是一个字符
let mark2 : Character = "!"
str + String(mark2)
str.append(mark2) //直接改变str这个变量
//
let englishLetter : Character = "A"
let chineseLetter : Character = "王"
let coolGuy : Character = "\u{1F60E}"
var coolLetters = "abc"
coolLetters.characters.count
var chineseLetters = "实际上"
chineseLetters.characters.count
var coolGuyss = "\u{1F60E}\u{1F60E}\u{1F60E}"
coolGuyss.characters.count
//swift中的字符串是基于unicode符的,更倾向于人类对字符的理解
//使得swift中对字符串的处理速度不够快
//str[0]//是不可以的
//获取字符串的字符
//String.Index
let startIndex = str.startIndex
startIndex
str[startIndex]//第一个字符
str[startIndex.advancedBy(5)]//第五个字符
let spaceIndex = startIndex.advancedBy(5)
spaceIndex
str[spaceIndex]
str[spaceIndex.predecessor()]//前一个字符
str[spaceIndex.successor()]//后一个字符
let endIndex = str.endIndex //endIndex不是字符串最后一个字符的索引,而在字符串最后一个字符之后的位置,
//[startIndex,endIndex)构成一个前闭后开的区间,整个字符串字符在startIndex .....endIndex-1的位置
str[endIndex.predecessor()]//最后一个字符
str[startIndex..<spaceIndex]
let rang = startIndex..<spaceIndex.predecessor()
str.replaceRange(rang, with: "hi")
str.appendContentsOf("!!!")
str.insert("?", atIndex: str.endIndex)
str.removeAtIndex(str.endIndex.predecessor())//删除最后一个字符
str
str.removeRange(str.endIndex.advancedBy(-2)..<str.endIndex)//删除最后两个字符
str.uppercaseString
str.lowercaseString
str.capitalizedString //词在首字母大学
str.containsString("hello")
str.hasPrefix("He")
str.hasSuffix("ft")
let s1 = "one third is \(1.0 / 3.0)"
//NSString as 桥接
let sa : String = NSString(format: "one third is %.2f",1.0/3.0) as String
var sn : NSString = "ONET"
sn.substringToIndex(4)
sn.substringFromIndex(4)
sn.substringWithRange(NSRange.init(location: 2, length: 2))
//NSString 不是基于unicode
sn.length
let s6 = "---- hello -----" as NSString
//去除字符串中的冗余
s6.stringByTrimmingCharactersInSet(NSCharacterSet(charactersInString: "-"))
s6
2.数组
使用let定义的数组是不可变数组
使用var定义的数组是可变数组
数组的初始化:数组的类型Array
方式一.泛型:<数组类型>
let array : Array<String> = ["1","2"]
方式二:
let name: [String] = ["why","y2"]
方式三:
let name3 = ["why","ys","lmj"]
可变数组
var name4 : [String] = ["why"]
添加元素
name4.append("y1")
定义一个空的数组
var name5 : [String] = Array()
var name6: [String] = [String]()
数组的基本操作:
数组中放任意类型可以使用NSObject或者AnyObject
var name7 : [AnyObject] = [AnyObject]()
name7.append("why")
name7.append(12)
name7.append(1.88)
移除:
移除之后一个元素
name7.removeLast()
移除特定下标的元素
name7.removeAtIndex(2)
移除全部元素
name7.removeAll()
修改元素
name7[0] = "ssss"
取出数组对应的元素
方法一:通过下标值来遍历
for i in 0..<name7.count{
print(name7[i])
}
方式二: for in遍历
for item in array{
print(item)
}
方式三:区间遍历
for item in name[0..<2]{
print(item)
}
数组的合并
let array1 = ["why" ,"+86",18]
let array2 = [1.88,"china"]
let array3 = array1 + array2
var array5 = [AnyObject]()
let array4 = [1.88, 19]
for item in array4{
array5.append(item)
}
for item in array3
{
array5.append(item)
}
array5
3.字典
字典的初始化
1.方式一
let dict : Dictionary<String,AnyObject> = ["name" : "why","age" : 18]
2.方式二
let dict2 : [String : AnyObject] = ["name" : "why","age" : 18]
方式三
let dict3 = ["name" : "why","age" : 18]
可变字典
1.方式1
var dict4 = Dictionary<String,AnyObject>()
2.方式二
var dict5 = [String : AnyObject]()
3.方式三
var dict6 = ["name" : "why","age" : 18]
字典操作
var dict7 = [String:AnyObject]()
添加元素
dict7["name"] = "why"
dict7["age"] = 17
dict7["height"] = 1.88
删除元素.删除元素,并返回删除的元素
dict7.removeValueForKey("age")
修改元素
注意:通过该方式修改的元素,如果有对应的键则修改,没有则添加
dict7["name"] = "123"
//取出
dict7["name"]
遍历字典
//1.遍历字典中的所有键
for key in dict7.keys{
print(key)
}
//2.遍历字典的所有值
for value in dict7.values{
print(value)
}
//3.遍历所有的键值对
for (key,value) in dict{
print(key)
print(value)
}
字典的合并
let dic1 = ["name" : "why","age" : 18]
var dic2 = ["phone": "110","height" : 1.88]
//注意:无论字典的类型是否一致,都不可以直接相加
for (key1,value1) in dic1{
dic2[key1] = value1
}
4.元祖
//定义元祖方式1
let a1 = ("why",18,1.88)
//方式2
let b = (name : "why",age: 18,height : 1.88)
//方式三
let (name1,age123,height1) = ("why",18,1.88)
//元祖的使用
let error = (404,"Not Found")
error.0
error.1
let error1 = (errorCode : 404,errorInfo: "not found")
error1.errorCode
error1.errorInfo
let (errorCode1 ,errorInfo1) = (404,"not fonund")
errorCode1
errorInfo1
5.可选型
1.在oc开发中,如果有一个变量暂停不使用,可以赋值0(基本数据类型)或者赋值为空(对象类型)
2.在swift中,nil也是一个特殊的类型,因为和真实类型不匹配不能赋值的(因为swift是强语言)
但是开发中赋值为nil,是在所难免的,所有推出了可选类型
可选类型取值
1.空值
2.有值
//定义可选类型,方式1 Optional<String>
var name20 : Optional<String>
name20 = "why"
//错误写法 类型不匹配
//let info = "my name is" + name20
print(name20) //optional("why")
//取出可选类型的值
//取值:可选类型 + !强制解包
print(name20!)
let info = "my name is" + name20!
let phoneNum :Optional<Int>
//2>方式二(语法糖)
var phoneNUm2 : String? = nil
phoneNUm2 = "+ 89 110"
//let phoneInfo = "my phoneNume" + phoneNUm2!
使用注意:如果一个可选类型里面没有值,强制解包会报错,所有在强制解包前要对类型进行判断,
//如果有值才进行解包
if phoneNUm2 != nil{
let phoneInfo = "my phoneNume" + phoneNUm2!
}
2.可选绑定:判断phoneNUm2是否有值
1>如果没有值,直接跳过
2>如果有值,将可选类型进行解包,并且将解包的后的值赋值给temponeNum
if let temponeNum = phoneNUm2{
print(temponeNum)
}
可选类似的使用,更加安全
