1、直接遍历字符串

var str = "大家好啊"

//1、直接遍历字符串
for c in str.characters{
    
    print(c)
    
}

2、字符串的拼接

//2、字符串的拼接
var str1="字符串1"
var str2 = "字符串2"

var str3 = str1+str2
print(str3)

3、字符串与其它类型拼接

//3、字符串与其它类型的拼接
var a=10
var b=3.14
var name = "哈哈"
var infoStr = "拼接后\(name)\(a)\(b)"
print(infoStr)

4、拼接字符串时，字符串的格式化 例如:显示: 02:08

//4、拼接字符串时，字符串的格式化  显示：02：08
var min=2
var second = 8
var timeString = String(format:"%02d:%02d",arguments:[min,second])
print(timeString)

5、字符串的截取

//5、字符串的截取
var urlString="http://www.baidu.com"

//先将String类型转换成NSString类型(String asNSString)

var header = (urlString as NSString).substring(to: 7)
print(header)

var middle=(urlString as NSString).substring(with: NSMakeRange(8,8))
print(middle)

var footer = (urlString as NSString).substring(from: 17)
print(footer)

6、判断字符串是否为空

//6、判断字符串是否为空
if footer.isEmpty{
    
    print("字符串为空")
}
else{
    print("字符串为\(footer)")
}