OC - 第四章 字符串

//                      第四章 字符串  //OC字符串:unichar(unicode码)组成 C语言:ASCII码  //不可变字符串 NSString 自身的长度以及内容都是不可变的  {            {                NSString *str1 = @"change";                str1 = @"IOS";                //@"change" = @"IOS";错误写法            }            //1.创建字符串的五种方式:            {                //第一种:                NSString *str = @"我勒个去";//语法糖  常量字符串 字面量                //第二种:                NSString *_str = [[NSString alloc]initWithString:@"我勒个去"];                //第三种: 通过一个字符串创建另外一个字符串 用的很少                NSString *str5 = [[NSString alloc]initWithString:str];                //第四种: 创建一个格式化字符串                NSString *str1 = [[NSString alloc]initWithFormat:@"%@, 大湿胸, 师傅被妖怪抓走了", str];//字符串拼接                //第五种:                NSString *str4 = [NSString stringWithFormat:@"%@ %@",str1, str1];//便利构造器            }            //2.字符串的常用方法            {                NSString *str = @"helloworld";                //1.从索引处开始截取,截取到字符串最后                NSString *result = [str substringFromIndex:5];                //2.从字符串开始截取到索引处,但是不包括索引处的字符                NSString *str1 = [str substringToIndex:5];                //3.截取指定范围内的字符                NSString *str2 = [str substringWithRange:NSMakeRange(2, 5)];                NSRange range = {2, 5};                NSString *str4 = [str substringWithRange:range];                //4.字符串的拼接                NSString *str3 = [str1 stringByAppendingString:str2];                //5.判断两个字符串是否相等                BOOL result1 = [str1 isEqualToString:str2];                //6.字符串比较的返回值, 升序, 相等, 降序                NSComparisonResult comparisonResult = [str1 compare:str2];                switch (comparisonResult) {                    case NSOrderedAscending:                        NSLog(@"str1比str2小");                        break;                    case NSOrderedSame:                        NSLog(@"str1和str2相等");                        break;                    case NSOrderedDescending:                        NSLog(@"str1比str2大");                        break;                    default:                        break;                }                //7.判断一个字符串是否以**开头                [str hasPrefix:@"Jen"];                //8.判断一个字符串是否以**结尾                [str hasSuffix:@"vi"];                //9.是否包含某个字符串                [str containsString:@" l"];                //10.大小写转换                NSString *strA = [str uppercaseString];                NSString *strB = [str lowercaseString];                //每个单词的首字母大写, 其余小写                NSString *strC = [str capitalizedString];                //11.替换                {                    //根据范围来替换                    NSString *str = @"苍苍老师.rmvb";                    NSString *str1 = [str stringByReplacingCharactersInRange:NSMakeRange(5, 4) withString:@"avi"];                    //将str中所有的"苍"替换成"波波"                    NSString *str2 = [str1 stringByReplacingOccurrencesOfString:@"苍" withString:@"波波"];                    NSLog(@"%@",str2);                }                //12.OC和C语言字符串的转换                {                    //将C字符串转换成OC字符串                    char *a = "iPhone";                    NSString *str = [[NSString alloc]initWithUTF8String:a];                    //将OC字符串转换成C字符串                    const char *q = [str UTF8String];                }        }   }  //可变字符串 NSMutableString 继承不可变字符串 引用不可用字符串方法仍需返回  {            //1.字符串的定义            NSMutableString *mStr = [[NSMutableString alloc]initWithString:@"ione"];            //2.插入字符串            [mStr insertString:@"Ph" atIndex:1];            //3.拼接字符串            [mStr appendString:@"6s"];            //4.根据范围删除            [mStr deleteCharactersInRange:NSMakeRange(3, 3)];            NSLog(@"%@",mStr);            //5.替换:替换后可以任意长度            [mStr replaceCharactersInRange:NSMakeRange(3, 2) withString:@"one6s plus"];  }