OC-NSString从文件中读取字符串

void test2(){
    NSString *path = @"/Users/gx/Desktop/test_utf8.txt";
    //NSString *str = [NSString stringWithContentsOfFile:path];
    //UTF-8编码
    NSString *str = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:nil];
    NSLog(@"%@",str);

    //GBK编码
    NSString *path2 = @"/Users/gx/Desktop/test_gbk.txt";
    NSString *str2 = [NSString stringWithContentsOfFile:path2 encoding:CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_18030_2000) error:nil];
    NSLog(@"%@",str2);

    //使用NSURL从文件中读取字符串
    NSURL *url = [NSURL URLWithString:@"file:///Users/gx/Desktop/test_utf8.txt"];
    NSString *str3 = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];
    NSLog(@"%@",str3);

    //使用NSURL读取远程文本
    NSURL *url2 = [NSURL URLWithString:@"http://www.baidu.com"];
    NSString *str4 = [NSString stringWithContentsOfURL:url2 encoding:NSUTF8StringEncoding error:nil];
    NSLog(@"%@",str4);
}