从Documents到NSData的文件

Question

我想从文档目录中获取一个文件到NSData对象，但如果我这样做，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，我总是得到一个例外，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！ 我之前创建了该文件：

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];

解决了它：

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

Answer 1

检查文件存在：

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

Answer 2

Swift 3版

let filePath = fileURL.path
if FileManager.default.fileExists(atPath: filePath) {
    if let fileData = FileManager.default.contents(atPath: filePath) {
        // process the file data
    } else {
        print("Could not parse the file")
    }
} else {
    print("File not exists")
}