9.swift-String字符串

//: Playground - noun: a place where people can play

import UIKit

//字符串在任何一个开发语言使用都有
//字符串的类型为String
//字符串为""
//String 是一个结构体,性能更高
//String 支持直接遍历
//swift提供了 String与NSString的转换

//定义字符串
let opration = "字符串";
print("%@",opration);

//遍历字符串
for i in opration {
    print(i);
}

//字符串之间拼接
let str1 = "💗";
let str2 = "听";
let str3 = str1 + str2;

//字符串与其他标识符之间的拼接
let name = "💗";
let age = 18;
let height = 1.80;
let result = "my name is \(name),my age is \(age), my height is \(height)";

//拼接字符串时,字符串格式化(02d表示不足两位用0代替)
let min = 2;
let second = 18;
let 格式化 = String().appendingFormat("%02d:%02d", min,second);

//截取字符串
let urlString = "www.baidu.com";
//将String转换为NSString类型 (String as NSString)
//substring(to: 3) 从头到3的下标,不包括3下标
let www = (urlString as NSString).substring(to: 3);
//substring(from: 10) 从10下标开始截取到最后,包含10下标
let com = (urlString as NSString).substring(from: 10);
//substring(with: NSMakeRange(4,5)) 从下标4开始截取,长度为5, 包含4下标
let baidu = (urlString as NSString).substring(with: NSMakeRange(4,5));


//全大写
let a = "abcdUP";
let A = a.uppercased();

//全小写
let aa = A.lowercased();

//开头
if a.hasPrefix("abc") {
    print("以什么开头");
}

//结尾
if a.hasSuffix("UP"){
    print("以什么结尾");
}