iphone - NSFileHandle fileHandleForReadingFromURL 抛出异常

Question

我只是想读取服务器上的文本文件。用于测试的文件目前是本地的。代码如下:

        NSString *pathToLocalFile = [NSHomeDirectory() stringByAppendingFormat:@"/Documents/dataVersion.txt"];
NSURL *URLToLocalFile = [[NSURL alloc]initFileURLWithPath:pathToLocalFile];

if (![[NSFileManager defaultManager] fileExistsAtPath:pathToLocalFile]) {
    NSFileManager *fileManager = [NSFileManager defaultManager];
    [fileManager createFileAtPath:pathToLocalFile contents:nil attributes:nil];
}

NSError *err = nil;
//NSURL *url = [[NSURL alloc] initWithString:@"http://stackoverflow.com/tags"];
    //using url also doesn't work
localFile = [[NSFileHandle alloc]fileHandleForReadingFromURL:URLToLocalFile error:&err];
localFileData = [localFile readDataToEndOfFile];

问题就在这里

[[NSFileHandle alloc]fileHandleForReadingFromURL:URLToLocalFile error:&err]; 

它总是抛出以下异常:

**NSInvalidArgumentException**, reason: **-[NSConcreteFileHandle fileHandleForReadingFromURL:error:]: unrecognized selector sent to instance.**  

URLToLocalFile 对象似乎没问题。

我在这里做错了什么？

Answer 1

这是一个类方法，您不需要分配实例。这样做:

[NSFileHandle fileHandleForReadingFromURL:URLToLocalFile error:&err];