iphone - 从文档文件到 NSData

Question

我想从文档目录中抓取一个文件到 NSData 对象中，但是如果我这样做，我的 NSData 总是 NIL:

filepath = [[NSString alloc] init];
filepath = [self.GetDocumentDirectory stringByAppendingPathComponent:fileNameUpload];
NSData *data = [[NSFileManager defaultManager] contentsAtPath:filepath];

-(NSString *)GetDocumentDirectory{
fileMgr = [NSFileManager defaultManager];
homeDir = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];

return homeDir;

在这一点上，我总是得到一个异常，我的数据是NIL:

[request addRequestHeader:@"Md5Hash" value:[data MD5]];

我检查过，没有文件，但我不知道为什么!我之前创建了那个文件:

NSMutableString *xml = [[NSMutableString alloc] initWithString:[xmlWriter toString]];

NSArray *paths = NSSearchPathForDirectoriesInDomains
(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];

//make a file name to write the data to using the documents directory:
NSMutableString *fileName = [NSMutableString stringWithFormat:@"%@/7-speed-",
                      documentsDirectory];

[xml writeToFile:fileName
          atomically:NO
            encoding:NSStringEncodingConversionAllowLossy
               error:nil];

通过以下方式解决:

[xml writeToFile:fileName
          atomically:YES
            encoding:NSUTF8StringEncoding
               error:nil];

Answer 1

检查文件是否存在:

if([[NSFileManager defaultManager] fileExistsAtPath:filepath)
{
   NSData *data = [[NSFileManager defaultManager] contentsAtPath:filepath];
}
else
{
   NSLog(@"File not exits");
}