Foundation 框架之——NSString、NSMutableString

 

    //字符串的创建
    NSString *s1 = @"Rose";
    
    // 作用相当于s1，基本不用
    // 警告：Using 'initWithString:' with a literal is redundant
    // 用“initWithString:“是多余的
    NSString *s2 = [[NSString alloc] initWithString:@"Rose"];
    

     NSString *s3 = [[NSString alloc]initWithFormat:@"age  is %d",20];
    
    // C字符串——>OC字符串
    // 注意"jack"前不要加@否则报错Implicit conversion of an Objective-C pointer to 'const char *' is disallowed with ARC
    // 隐式转换的objective - c指针到弧‘const char *’无效
    NSString *s4 = [[NSString alloc] initWithUTF8String:"jack"];
    // OC字符串——>c字符串
    const char *cs = [s4 UTF8String];
    
    // NSUTF8StringEncoding 用到中文就可以用这种编码
    NSString *s5 = [[NSString alloc]initWithContentsOfFile:@"/Users/scjy/Desktop/作业/作业/图像面积/图像面积/main.m" encoding:NSUTF8StringEncoding error:nil];
    
    // URL ：资源路径
    // 协议头：//路径
    // file://
    // ftp://
    
    NSURL *url = [[NSURL alloc] initWithString:@"file:///Users/scjy/Desktop/OC/作业/作业/图像面积/图像面积/main.m"];
    NSString *s6 = [[NSString alloc]initWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];
    
    NSLog(@"s6:%@",s6);
    
   /*
    一般都有一个类方法跟对象方法配对
    [ NSURL URLWithString:<#(NSString *)#>];
    [NSString stringWithFormat:<#(NSString *), ...#>];
    [NSString stringWithContentsOfFile:<#(NSString *)#> encoding:<#(NSStringEncoding)#> error:<#(NSError *__autoreleasing *)#>];
    
    */

 

atomically原子性参数为YES时文件不存在且写入失败是不创建文件

    // 字符串的导出
    [@"jadfjallf" writeToFile:@"/Users/scjy/Desktop/OC/t.txt" atomically:YES encoding:NSUTF8StringEncoding error:nil];
    
    NSString *str = @"sdfkafads";
    NSURL *url = [NSURL fileURLWithPath:@"/Users/scjy/Desktop/OC/tr.txt"];
    [str writeToFile:url atomically:YES encoding:NSUTF8StringEncoding error:nil];

 

 

 

    NSMutableString *s1 = [NSMutableString stringWithFormat:@"my age is 10"];
    // 拼接内容到s1的后面
    [s1 appendString:@" 11 12"];
    
    // 获取is的范围
    NSRange range = [s1 rangeOfString:@"is"];
    [s1 deleteCharactersInRange:range];
    
    NSString *s2 = [NSString stringWithFormat:@"age is 10"];
    // 把s2复制一份后和11 12 拼接返回给s3，实际上s2没有变化
    NSString *s3 = [s2 stringByAppendingString:@" 11 12"];
    
    
    NSLog(@"s1=%@, s2=%@", s1, s2);

        //快速创建一个字符串常量
        NSString *str01 = @"This is a string";
        NSLog(@"字符串str1：%@",str01);
        
        //快速创建一个空字符串
        // 使用对象实例创建
        NSString *str02 = [[NSString alloc]init];
        // 使用类方法创建
        NSString *str03 = [NSString string];
        // str04和str02、str03是不一样的，str04是指针为空
        NSString *str04 = nil;
        NSLog(@"str02:%@ str03:%@ str04:%@",str02,str03,str04);
        
        // 根据已有的字符串创建新的（常量区）内容一样的话，地址也一样，即str5、str6的地址一样
        // 使用实例对象方法创建
        NSString *str05 = [[NSString alloc]initWithString:str01];
        // 使用类对象方法创建
        NSString *str06 = [NSString stringWithString:str01];
        NSLog(@"str05:%@ str06:%@",str05,str06);
        
        
        NSString *str1 = @"asddffg";
        // 创建新的字符串（堆区）
        NSString *str2 = [[NSString alloc]initWithFormat:@"字符串%d",2];
        NSString *str3 = [NSString stringWithFormat:@"字符串%d",2];
        
        BOOL isEquale = [str2 isEqualTo:str3];
        if (isEquale) {
            NSLog(@"str2 and str3 is same string");
        }
        
        NSString *str4 = @"this is a string";
        NSLog(@"str4 length is %d",(int)str4.length);
        
        NSLog(@"全部转换成大写%@",[str4 uppercaseString]);
        NSLog(@"全部转换成小写%@",[str4 lowercaseString]);
        NSLog(@"首字母大写%@",[str4 capitalizedString]);
        
        NSString *str5 = @"3.1415926";
        double pi = [str5 doubleValue];
        NSLog(@"pi is %lf",pi);
        
        NSString *str6 = @"[00:15]:我 [00:18]:想 [00:19]:大 [00:21]:声";
        NSCharacterSet *character = [NSCharacterSet characterSetWithCharactersInString:@"[]0123456789:"];
        NSArray *str8 = [str6 componentsSeparatedByCharactersInSet:character];
        NSArray *str7 = [str6 componentsSeparatedByString:@" "];
        NSLog(@"%@
%@",str7,str8);
        
        // 从某处开始截取
        NSString *str9 = [str4 substringFromIndex:2];
        // 根据自定义区域截取一段字符串
        NSString *str10 = [str4 substringWithRange:NSMakeRange(2, 5)];
        // 从开始截取到某处
        NSString *str11 = [str4 substringToIndex:2];
        NSLog(@"str9:%@
str10:%@
str11:%@",str9,str10,str11);
        
        // 包含
        NSString *str12 = @"string";
        NSRange range = [str4 rangeOfString:str12];
        NSLog(@"%@",NSStringFromRange(range));
        NSLog(@"%d",[str4 containsString:str12]);
        // 判断开头
        NSLog(@"%d",[str4 hasPrefix:@"this"]);
        // 判断结尾
        NSLog(@"%d",[str4 hasSuffix:@"string"]);
        
//        BOOL bool = 0;
        
        NSMutableString *mstr1 = [NSMutableString stringWithFormat:@"Hello China"];
        // 插入字符
        [mstr1 insertString:@" Welcome" atIndex:5];
        // 字符串的的替换
        [mstr1 replaceCharactersInRange:NSMakeRange(6, 7) withString:@"Good"];
        // 删除
        [mstr1 deleteCharactersInRange:NSMakeRange(6, 4)];
        
        NSLog(@"%@",mstr1);