(String)字符串的简单应用

1. 字符串的截取

    NSString *str = @"hello world Wellcome";
    //从哪个位置起，截取多少位
    NSString *str1 = [str substringWithRange:NSMakeRange(3, 6)];
    //从某个位置起，一直到末尾
    NSString *str2 = [str substringFromIndex:5];
    //从开始截取到某个位置
    NSString *str3 = [str substringToIndex:5];

2. 字符串的比较

    NSString *str = @"hello";
    if ([str isEqualToString:@"hello"]){
        NSLog(@"isEqual");
    }

3. 字符串包含...内容(以...结尾，以...开头)

    NSString *str = @"http://www.xxx.com";
    //字符串包含...
    if ([str containsString:@"xxx"]) {
        NSLog(@"包含xxx");
    }
    //字符串以...结尾
    if ([str hasSuffix:@".com"]) {
        NSLog(@"以.com结尾");
    }
    //字符串以...开头
    if ([str hasPrefix:@"http:"]) {
        NSLog(@"以http:开头");
    }

4. 查询字符串所在位置

    NSString *str = @"hello world welcome";
    NSRange range = [str rangeOfString:@"welcome"];
    //当字符串不存在时
    if (range.location == NSNotFound) {
        NSLog(@"no found");
    }
    //字符串所在位置
    NSLog(@"%ld", range.location);

5. 字符串的连接

    //1. 连接时不会自动加"/"
    NSString *finalPath1 = [basePath stringByAppendingString: @"/Documents"];
    //2. 连接时会自动加上"/"
    NSString *finalPath2 = [basePath stringByAppendingPathComponent:@"Documents"];
    //3. 最常用的连接
    NSString *finalPath3 = [NSString stringWithFormat:@"%@/Documents", basePath];

6. 字符串与整数之间的转换

    NSString *a = @"55";
    //将字符串转换成整数
    NSInteger b = a.integerValue;
    //将整数转化成数组
    NSString *a1 = [NSString stringWithFormat:@"%ld", b];

7. 将字符串的形式统一为大写或小写或首字母大写

    NSString *name = @"zhangSAN liSI";
    //将字符串统一转换成小写
    NSString *trueName1 = [name lowercaseString];
    //将字符串统一成大写形式
    NSString *trueName2 = [name uppercaseString];
    //每个单词的首字母大写
    NSString *trueName3 = [name capitalizedString];

8. NSData和NSString类型的转换

    NSString *str = @"hello world";
    //将NSString类型转换成NSData类型
    NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];
    //将NSData类型转换成NSString类型
    NSString *data_string = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];

9. 去掉字符串之前的空格符号

    NSString *userName = @"         zhangsan";
    //去掉字符串前面的所有空格符号
    NSString *finalUserName = [userName stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];

10. 屏蔽指定单词

    NSString *str = @"hello world welcome";
    NSString *secrStr = [str stringByReplacingOccurrencesOfString:@"world" withString:@"*****"];
    NSLog(@"%@", secrStr);
    
    NSString *sourceStr = @"welcome";
    NSString *target;
    NSInteger length = sourceStr.length;
    NSMutableArray *stars = [NSMutableArray array];
    for (int i = 0; i < length; i++) {
        [stars addObject:@"*"];
    }
    target = [stars componentsJoinedByString:@""];
    NSString *secrStr2 = [str stringByReplacingOccurrencesOfString:sourceStr withString:target];
    NSLog(@"%@", secrStr2);

11. 将NSString写入文件

    NSString *str = @"牛逼呀！！！！";
    NSString *path = @"/Users/apple/Desktop/str.txt";
    [str writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:nil];
    NSString *result = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:nil];

12. 数组和字符串之间的转换

    NSString *str = @"asd,weasd,dsadq";
    //以","分割成数组
    NSArray *arr = [str componentsSeparatedByString:@","];
    //以"_"合并成字符串
    NSString *str2 = [arr componentsJoinedByString:@"_"];

13. 获取左边栏文件的路径

    //第一个参数是文件名，第二个参数是文件类型
    NSString *lyricsPath = [[NSBundle mainBundle] pathForResource:@"谢谢你的爱" ofType:@"lrc"];