字符串的基本使用

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文件读取

	NSError *error = nil;
	NSString *path = @"/Users/releasemr./Desktop/content.txt";
	
	NSString *str  = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:&error];
	
	if (error == nil) {
	    NSLog(@"str == %@",str);
	}else{
	    NSLog(@"error = %@",[error localizedDescription]);
	}
	
	NSString *path2 = @"file:///Users/releasemr./Desktop/content.txt";
	//如果path中有中文
	path2 = [path2 stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
	
	NSURL *url = [NSURL URLWithString:path2];
	NSURL *url2 = [NSURL fileURLWithPath:@"/Users/releasemr./Desktop/content.txt"];
	
	NSString *str2 = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];
	
	NSLog(@"str2 == %@",str2);
	
	//文件写入
	NSString *str3 = @"hello world33";
	NSString *path3 = @"/Users/releasemr./Desktop/content2.txt";
	
	BOOL flag = [str3 writeToFile:path3 atomically:YES encoding:NSUTF8StringEncoding error:nil];
	
	NSLog(@"flag == %i",flag);
	
	NSString * path33 = @"file:///Users/releasemr./Desktop/content2.txt";
	//        NSString *url3 = [NSURL URLWithString:path33];
	NSString *url3 = [NSURL fileURLWithPath:path33];
	[str3 writeToURL:url3 atomically:YES encoding:NSUTF8StringEncoding error:nil];

字符串比较

	NSString *str1 = @"abc";
	NSString *str2 = @"ABC";
	
	//比较的是内容
	BOOL flag = [str1 isEqualToString:str2];
	NSLog(@"flag == %i",flag);
	
	//比较的是地址
	flag = (str1 == str2);
	NSLog(@"flag == %i",flag);
	
	switch ([str1 caseInsensitiveCompare:str2]) {
	    case NSOrderedAscending:
	        NSLog(@"str1小于str2");
	        break;
	case NSOrderedSame:
	       NSLog(@"str1等于str2");
	        break;
	    case NSOrderedDescending:
	        NSLog(@"str1大于str2");
	        break;
	
	    default:
	        break;
	}

字符串搜索

     NSString *str = @"https://www.baidu.com";

     //判断是否以什么开头
     if ([str hasPrefix:@"https"]) {
         NSLog(@"是一个URL");
     }else{
          NSLog(@"不是一个URL");
     }

     //判断是否以什么结尾
     if ([str hasSuffix:@".com"]) {
         NSLog(@"是以.com结尾");
     }else{
         NSLog(@"不是以.com结尾");
     }

     //判断是否包含baidu
     NSRange range = [str rangeOfString:@"baidu"];

//        if (range.location == NSNotFound) {
     if (range.location == 0) {
         NSLog(@"不包含baidu");
     }else{
         NSLog(@"location == %lu,length == %lu",range.location,range.length);
     }

字符串截取

    NSString *str = @"<head>百度</head>";
    NSUInteger loaction = [str rangeOfString:@">"].location + 1;
    NSUInteger length = [str rangeOfString:@"</"].location - loaction;
    NSRange range = NSMakeRange(loaction, length);
    NSString *newStr = [str substringWithRange:range];
    NSLog(@"newStr == %@",newStr);

    //从指定位置截取,一直截到末尾
    NSString *str2 = [str substringFromIndex:6];
    NSLog(@"str2 == %@",str2);

    //从开头开始截,一直截到什么位置
    NSString *str3 = [str substringToIndex:6];
    NSLog(@"str3 == %@",str3);

字符串替换

   NSString *str = @"https://www.baidu.com";
   NSString *newStr = [str stringByReplacingOccurrencesOfString:@"baidu" withString:@"ali"];
   NSLog(@"newStr == %@",newStr);

   //去空格
   NSString *str2 = @"https   ://www.   baidu.  com";
   NSString *newStr2 = [str2 stringByReplacingOccurrencesOfString:@" " withString:@""];
   NSLog(@"newStr2 == %@",newStr2);

   //替换首位
   NSString *str3 = @"  https://www.baidu.com  ";
   NSCharacterSet *set = [NSCharacterSet whitespaceCharacterSet];
   NSString *newStr3 = [str3 stringByTrimmingCharactersInSet:set];
   NSLog(@"newStr3 == %@",newStr3);

字符串和路径

    NSString *str = @"/Users/releasemr./Desktop/content.txt";

    if ([str isAbsolutePath]) {
        NSLog(@"是绝对路径");
    }else{
        NSLog(@"不是绝对路径");
    }

    //获取文件路径中的最后一个目录
    NSString *newStr = [str lastPathComponent];
    NSLog(@"newStr == %@",newStr);

    //给文件路径添加一个目录
    NSString *newStr2 = [str stringByAppendingPathComponent:@"xml"];
    NSLog(@"newStr2 == %@",newStr2);

    //删除文件路径中的最后一个目录
    NSString *newStr3 = [str stringByDeletingLastPathComponent];
    NSLog(@"newStr3 == %@",newStr3);

    //获取文件路径的扩展名
    newStr = [str pathExtension];
    NSLog(@"newStr == %@",newStr);

    //删除文件路径的扩展名
    newStr = [str stringByDeletingPathExtension];
    NSLog(@"newStr == %@",newStr);

    //给文件路径添加一个扩展名
    newStr = [str stringByAppendingPathExtension:@"jpg"];
    NSLog(@"newStr == %@",newStr);

字符串转换

    //将字符串转换为大写
    NSString *str = @"aBc";
    NSString *newStr = [str uppercaseString];
    NSLog(@"newStr == %@",newStr);

    //将字符串转换为小写
    newStr = [str lowercaseString];
    NSLog(@"newStr == %@",newStr);

    //将字符串首字母转换为大写
    newStr = [str capitalizedString];
    NSLog(@"newStr == %@",newStr);

    //字符串与基本数据类型的转换
    NSString *str1 = @"110";
    NSString *str2 = @"119";

    int value1 = [str1 intValue];
    int value2 = [str2 intValue];
    NSLog(@"sum == %i", value1 + value2);

    //c语言与oc字符串之间的转换
    char *cStr = "baidu";
    NSString *str3 = [NSString stringWithUTF8String:cStr];
    NSLog(@"str == %@",str3);

    NSString *newStr3 = @"baidu";
    const char *cStr2 = [newStr3 UTF8String];
    NSLog(@"str == %s",cStr2);
字符串的基本使用字符串的基本使用 延成 发布了139 篇原创文章 · 获赞 19 · 访问量 2万+ 私信 关注
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