运算符
- 赋值
let a = 2- 操作符
a b
a = a //swift4 废弃
a =2
a * b
a / b //b不能为0
a % b // b 不能为0
let d = 5.2,e = 1.7
d / e
d % e //也能使用浮点型进行求余
Int.max //查看Int类型支持的最大值
Int.min //查看Int类型支持的最小值
var c = 2
c =1
//条件运算符
var score = 62
var rate = score > 60 ? "合格":"不合格"- nil聚合运算符
var userNickName :String?
userNickName = "imagine"
let outputName:String = userNickName != nil ? userNickName! : "Guest"
print("hello," outputName)
//改进
let outputName:String = userNickName ?? "Guest"- 区间运算符
//闭区间 [a,b] 表示：a...b
//前闭后开区间 [a,b) 表示：a..<b- for-in
for index in 1..<10
{
index
//index = 3 //error
}
//arr.count数组长度
let names = ["aaa","bbb","ccc"];
for i in 0..<names.count
{
names[i]
}- 逻辑运算符
!a //非
a && b //与
a || b //或
区别“位运算符”
a & b //按位与
a | b //按位或字符串
- String和Character
//变量与常量字符串
var str1 = "aaa"
let str2 = "bbb"
//创建空字符串
var emptyString = ""
var str2 = String()
//字符串遍历
var str = "hello"
for c in str
{
print(c)
}
//定义一个字符
var ch:Character = "!"
str.append(ch) //在字符串后面拼接一个字符
//字符串之间拼接
var str2 = "!!!"
str = str2 //hello!!!!- String操作
var str = "Hello"
//拼接
str "imagine"
str
str = "imagine"
str
//字符串插值
print("123 (str)")
//字符串比较
//按字典顺序比较，不考虑长度
let str_a = "abc"
let str_b = "abc"
str_a == str_b
let str_c = "abd"
str_a < str_c
//前缀 Prefix 与 后缀 Suffix
//.hasPrefix and .hasSuffix
//统计前缀有 b 的个数
let names = [
"a 1.aaa",
"b 1.bbb",
"b 2.bbb",
"b 3.ccc"
]
var count = 0
for name in names {
if name.hasPrefix("b"){
count = count //3 times
}
}- 导入Foundation 使用字符串的更多功能
import Foundation
var str = "hello"
str.capitalized //Hello 首字母大写
str.uppercased() //字母大写
str.lowercased() //字母小写
//split
var str2 = "hello hhh"
str2.components(separatedBy: " ")
