NSString类(1)

    //1.快速创建
    NSString  *str1 = @"白日依山尽";
    
    //2.用alloc创建
    NSString *str2 = [[NSString alloc]initWithString:@"黄河入海流"];
    
    //3.用格式化符创建字符串
    NSString *str3 = [[NSString alloc]initWithFormat:@"%@",@"欲穷千里目"];
    
    //4.类方法格式化符创建
    NSString *str4 = [NSString stringWithFormat:@"%@",@"更上一层楼"];

    //比较字符串是否相同 方法一     比较的是字符串中的内容
    BOOL count1 = [str1 isEqualToString:str2];
    NSLog(@"count1 = %d",count1);
    
    //比较字符串是否相同 方法二     比较的是字符串的地址
    BOOL count2 = (str2 == str3);
    NSLog(@"count2 = %d",count2);
    
    //比较字符串大小
    NSComparisonResult result = [str3 caseInsensitiveCompare:str4];
    if(result == NSOrderedAscending)
        NSLog(@"升序");
    else if(result == NSOrderedSame)
        NSLog(@"相等");
    else if (result == NSOrderedDescending)
        NSLog(@"降序");

    //获取到字符串长度
    NSInteger strLength = [str4 length];
    NSLog(@"strLength = %ld",strLength);

    //字符串的转换
    NSString *str5 = @"Hello World";
    
    //全部转换成小写
    NSLog(@"str5 = %@",[str5 lowercaseString]);
    
    //全部转换成大写
    NSLog(@"str5 = %@",[str5 uppercaseString]);
    
    //每个单词的首字母大写，其余小写
    NSLog(@"str5 = %@",[str5 capitalizedString]);

    //转换成整型
    NSString *str6 = @"3456789";
    NSLog(@"str6 = %ld",[str6 integerValue]);
    
    //转换成浮点型
    NSString *str7 = @"12321.34832";
    NSLog(@"str7 = %lf",[str7 floatValue]);
    
    //转换成布尔类型
    NSString *str8 = @"1";
    NSLog(@"str8 = %d",[str8 boolValue]);

    //分割字符串
    NSString *str9 = @"aa,bbb,cc,dddd,e,ffff";
    NSArray *arr = [str9 componentsSeparatedByString:@","];
    
    //遍历数组
    for(NSString *s1 in arr){
        NSLog(@"s1 = %@",s1);
    }
    
    NSString *str10 = @"abcdefg";
    char s2 = [str10 characterAtIndex:2];
    NSLog(@"s2 = %c",s2);
    
    //截取字符串
    NSString *str11 = @"you are my sunshine";
    
    //截取到index之前的字符
    NSString *substr1 = [str11 substringToIndex:3];
    NSLog(@"sub1 = %@",substr1);
    
    //从index位置开始往后截取
    NSString *substr2 = [str11 substringFromIndex:8];
    NSLog(@"sub2 = %@",substr2);
    
    //利用NSRange来截取某个范围的字符
    NSRange range = NSMakeRange(5, 13);
    NSString *substr3 = [str11 substringWithRange:range];
    NSLog(@"sub3 = %@",substr3);

    //拼接字符串
    NSString *str12 = @"少年易老学难成";
    NSString *str13 = @"一寸光阴不可轻";
    
    //方法一
    NSString *string1 = [NSString stringWithFormat:@"%@ %@",str12,str13];
    NSLog(@"string1 = %@",string1);
    
    //方法二
    NSString *string2 = [str12 stringByAppendingString:str13];
    NSLog(@"string2 = %@",string2);
    
    //方法三
    NSString *string3 = [str13 stringByAppendingFormat:@"  %@",str13];
    NSLog(@"string3 = %@",string3);