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  • iOS中的字符串NSString

    创建一个字符串对象:

    NSstring * str1 = @"hello world";
    NSString * str = [[NSString alloc]initWithString:@"hello world!"];
    NSString * str_1 = [[NSString alloc]initWithUTF8String:"hello world"];//把C的字符串转化为OC的字符串
    int a = 123;

    NSString * str_3 = [[NSString alloc]initWithFormat:@"a = %d %s%@", a, "abcd", @"efg"];//用格式化字符串初始化


    //可完毕字符串的拼接以及完毕C的字符串与OC的字符串的转化
    NSString * str1 = [NSString stringWithString:@"hello world"];
    NSString * str2 = [NSString stringWithUTF8String:"hello world"];
    NSString * str3 = [NSString stringWithFormat:@"%s","hello world"];
    NSstring * str1 = @"hello";
    NSString * str = [[NSString alloc]initWithString:@"hello world!"];

    NSString * str_1 = [[NSString alloc]initWithUTF8String:"hello world"];//把C的字符串转化为OC的字符串


    int a = 123;

    NSString * str_3 = [[NSString alloc]initWithFormat:@"a = %d %s%@", a, "abcd", @"efg"];//用格式化字符串初始化


    字符串转化:

    NSString * str = @"hello";
    const char *p = [str UTF8String];将OC字符串转化为C的字符串
     
    str = @"123";
    int a = [str intValue];//将数字串转化成整型数据
        [str floatValue];//将数字串转化成float型
            [str doubleValue];//将数字串转化成double型
    NSString * str = @"hello";
    const char *p = [str UTF8String];将OC字符串转化为C的字符串
     
    str = @"123";
    int a = [str intValue];//将数字串转化成整型数据
        [str floatValue];//将数字串转化成float型

            [str doubleValue];//将数字串转化成double型


    经常使用的NSString :

    NSLog(@"%ld",[str1 length]);   //求字符串长度
     
    NSLog(@"%c", [str1 characterAtIndex:1]);//获取字符串中的字符
     
    BOOL ret =  [str1 isEqualTo:str2];//比較两个字符串是否相等,相等返回YES(1),不相等返回NO(0)   (BOOL   YES(1)  NO(0))
     
    long ret1 = [str1 compare:str2];//比較两个字符串的大小,str1大于 返回1  相等返回0   小于返回-1
     
    long ret2 = [str1 caseInsensitiveCompare:str2];//不区分大写和小写比較字符串大小
     
    NSString * ptr = [str2 uppercaseString];//将字符串中的全部小写字符转换成大写 不改变原来的字符串
     
    ptr = [str1 lowercaseString];//将字符串中的全部大写字符转换成小写 不改变原来的字符串
     
    ptr = [str3 capitalizedString];//将字符串中出现的第一个字母转换成大写,其余字母小写
     
    NSString * str4 = @"hello world";
     
    NSRange range = [str4 rangeOfString:@"wr"];//查找子串,找不到返回NSNotFound 找到返回location和length
     
    if (range.location != NSNotFound) {
     
        NSLog(@"%ld %ld",range.location, range.length);
     
    }
     
    NSString * str5 = @"helloworld";
     
    NSString * ptr1 = [str5 substringToIndex:4];//字符串抽取 从下标0開始到4 不包含4
     
    NSString * ptr2 = [str5 substringFromIndex:5];//从下标5開始抽取到字符串结束 包含5
     
    NSRange range1 = {4,3};//结构体初始化
     
    NSString * ptr3 = [str5 substringWithRange:range1];//在range指定范围内抽取
     
    NSString * ptr4 = [str5 substringWithRange:NSMakeRange(4,3)];//NSMakeRange能够生成一个结构体
     
     
     
    NSString * str = @"www.baidu.com";
     
    BOOL ret = [str hasPrefix:@"www"];//推断字符串是否以指定字符串开头
     
     
     
    NSString * str1 = @"1.txt";
     
    BOOL ret1 = [str hasSuffix:@".txt"];//推断字符串是否以指定的字符串结尾
     
     
     
    NSMutableString可变字符串(动态添加和降低的)   继承于NSString能够使用NSString的全部方法
     
    NSMutableString * str =  [[NSMutableString alloc]initWithString:@"hello"];//将不可变的字符串转换为可变的字符串
     
    [str insertString:@"123" atIndex:1];//在指定下标(不要越界)位置插入NSString类型字符串
     
    [str appendString:@"123"];//在字符串末尾追加字符串
     
    [str deleteCharactersInRange:NSMakeRange(0, 2)];//从指定下标删除length个字符
     
    [str setString:@"baidu"];//改动字符串亦称对该可变字符串赋值
     
    [str replaceCharactersInRange:NSMakeRange(3, 1) withString:@"ios"];//将指定下标位置的length个字符替换为指定的字符串
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  • 原文地址:https://www.cnblogs.com/mfrbuaa/p/5113826.html
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