UIDocument loadFromContents應該返回一個NSFileWrapper;返回NSConcreteData

Question

我正在製作一個文本編輯器應用程序，將其文檔的每個文檔存儲爲NSFileWrapper目錄，文檔文本和文檔標題作爲目錄中的單獨文件。我期望部分loadFromContents: (id) contents是一個NSFileWrapper，但事實並非如此。我的代碼如下（它屬於UIDocument的子類）：

// loads document data to application data model 

- (BOOL) loadFromContents:(id)contents ofType:(NSString *)typeName error:(NSError *__autoreleasing *)outError { 
    // from the contents, extract it so that we have the properties initialized 
    self.fileWrapper = (NSFileWrapper *) contents; 
    NSLog(@"%@", [contents class]); //** returns NSConcreteData 

    // get the fileWrapper's children 
    NSDictionary *contentsOfFileWrapper = [contents fileWrappers]; 

    // assign things to the document! 
    // can also be done lazily through getters 

    self.text = [contentsOfFileWrapper objectForKey:TEXT_KEY]; 
    self.title = [contentsOfFileWrapper objectForKey:TITLE_KEY]; 
    if ([self.delegate respondsToSelector:@selector(noteDocumentContentsUpdated:)]){ 
     [self.delegate noteDocumentContentsUpdated:self]; 
    } 
    return YES; 
} 

當我試圖調用這個方法，我得到這個錯誤：

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSConcreteData fileWrappers]: unrecognized selector sent to instance 0x9367150'

下面是我contentsForType:功能，如果有幫助：

- (id) contentsForType:(NSString *)typeName error:(NSError *__autoreleasing *)outError { 
    if (!self.fileWrapper) { 
     self.fileWrapper = [[NSFileWrapper alloc] initDirectoryWithFileWrappers:nil]; 
    } 

    NSDictionary *childrenFileWrappers = [self.fileWrapper fileWrappers]; 

    // now if we have a text but it is not represented, in the file wrapper, put it in. Same with the images. 
    if ([childrenFileWrappers objectForKey:TEXT_KEY] == nil && self.text != nil) { 
     NSData *textData = [self.text dataUsingEncoding:kCFStringEncodingUTF16]; 
     NSFileWrapper *textFileWrapper = [[NSFileWrapper alloc] initRegularFileWithContents:textData]; 
     [textFileWrapper setPreferredFilename:TEXT_KEY]; 
     [self.fileWrapper addFileWrapper:textFileWrapper]; 
    } 

    if ([childrenFileWrappers objectForKey:TITLE_KEY] == nil && self.title != nil) { 
     NSData *titleData = [self.title dataUsingEncoding:kCFStringEncodingUTF16]; 
     NSFileWrapper *titleFileWrapper = [[NSFileWrapper alloc] initRegularFileWithContents:titleData]; 
     [titleFileWrapper setPreferredFilename:TITLE_KEY]; 
     [self.fileWrapper addFileWrapper:titleFileWrapper]; 
    } 

    return self.fileWrapper; 

} 

謝謝！

Answer 1

我解決了這個問題。我的文檔文件夾中有一個.DS_Store文件，它將結果搞亂了。一旦我添加if語句來排除一切工作正常。