String的创建与拼接

截屏2022-03-06 下午2.45.10.png

String的插入与删除

var str:String = "1_2"
print(str,str.startIndex,str.endIndex)
 // 1 Index(_rawBits: 1) Index(_rawBits: 65537)

从上面打印可以看出，startIndex与endIndex与我们所认知的是不同的，OC里可能startIndex是0,endIndex是2,但是在Swift里就不一样了

        var str:String = "1_2"
        // print(str,str.startIndex,str.endIndex)
        str.insert("_", at: str.endIndex)
        print(str) // 1_2_
        str.insert(contentsOf: "3_4", at: str.endIndex)
        print(str) // 1_2_3_4
        str.insert(contentsOf: "666 ", at: str.index(after: str.startIndex))
        print(str) // 1666 _2_3_4
        str.insert(contentsOf: "888", at: str.index(before: str.endIndex))
        print(str) // 1666 _2_3_8884
        str.insert(contentsOf: "hello", at: str.index(str.startIndex, offsetBy: 4))
        print(str) // 1666hello _2_3_8884
        
        str.remove(at: str.firstIndex(of: "1")!)
        print(str) // 666hello _2_3_8884
        str.removeAll() {
            $0 == "6"
        }
        print(str) // hello _2_3_8884
        let range = str.index(str.endIndex, offsetBy: -4)..<str.index(before: str.endIndex)
        str.removeSubrange(range)
        print(str) // hello _2_3_4

Substring

截取字符串

        var str = "1_2_3_4_5"
        var substr1 = str.prefix(3)
        print(substr1) // 1_2
        var substr2 = str.suffix(3)
        print(substr2) // 4_5
        var range = str.startIndex..<str.index(str.startIndex, offsetBy: 3)
        var substr3 = str[range];
        print(substr3) // 1_2
        print(substr3.base) // 1_2_3_4_5
        
        var str2 = String(substr3)
        print(str2) // 1_2

截屏2022-03-06 下午7.14.58.png

String与Character

for c in "jack" { // c是Character类型
    print(c)
}

var str = "jack"
// c是Character类型
var c = str[str.startIndex]

String与NSString

String与NSString之间可以随时随地桥接转换

如果你觉得String的API过于复杂难用，可以考虑将String转为NSString

var str1:String = "Jack"
var str2:NSString = "rose"

var str3 = str1 as NSString
var str4 = str2 as String


var str5 = str3.subString(with:NSRange(location:0, length:2))
print(str5) // ja