cocoa - NSDocument 和 writeToURL :ofType:error: 的问题

Question

我正在开发一个基于文档的应用程序，并且我想使用文档包作为我的文件格式。为此，我需要重写的 NSDocument 方法似乎是
-writeToURL:ofType:error:.

有时它会起作用，但仅在某些条件下有效。例如，此代码有效:

- (BOOL)writeToURL:(NSURL *)absoluteURL ofType:(NSString *)typeName error:(NSError **)outError
{   
    NSFileWrapper *wrapper = [[NSFileWrapper alloc] initDirectoryWithFileWrappers:nil];
    [wrapper addRegularFileWithContents:[@"please work" dataUsingEncoding:NSUTF8StringEncoding] preferredFilename:@"foobar"];
    [wrapper writeToURL:absoluteURL options:NSFileWrapperWritingAtomic originalContentsURL:nil error:outError];

    NSDictionary *metadata = [NSDictionary dictionaryWithObject:@"0.1" forKey:@"Version"];
    NSURL *mdURL = [NSURL fileURLWithPath:[[absoluteURL path] stringByAppendingPathComponent:@"SiteInfo.plist"]];
    [metadata writeToURL:mdURL atomically:YES];

    return YES; 
}

但是，这段代码没有(与上面相同，但去掉了 NSFileWrapper 位):

- (BOOL)writeToURL:(NSURL *)absoluteURL ofType:(NSString *)typeName error:(NSError **)outError
{   
    NSDictionary *metadata = [NSDictionary dictionaryWithObject:@"0.1" forKey:@"Version"];
    NSURL *mdURL = [NSURL fileURLWithPath:[[absoluteURL path] stringByAppendingPathComponent:@"SiteInfo.plist"]];
    [metadata writeToURL:mdURL atomically:YES];

    return YES; 
}

上面的代码将这个神秘的错误放入控制台(“Lithograph”是我的应用程序的名称，“.site”是包扩展名):

NSDocument could not delete the temporary item at file://localhost/private/var/folders/qX/qXL705byGmC9LN8FpiVjgk+++TI/TemporaryItems/(A%20Document%20Being%20Saved%20By%20Lithograph%207)/Untitled%20Site.site. Here's the error:
Error Domain=NSCocoaErrorDomain Code=4 UserInfo=0x10059d160 "“Untitled Site.site” couldn’t be removed."

我是否必须在原始 URL 中写入一些内容才能将其他文件添加到包中？

Answer 1

如果您要从文档创建文件包装器，则应使用 -fileWrapperOfType:error: 而不是 -writeToURL:ofType:error:。

您将为 Info.plist 文件构造一个文件包装器，将其插入文件夹文件包装器，然后返回文件夹包装器:

- (NSFileWrapper *)fileWrapperOfType:(NSString *)typeName error:(NSError **)outError
{   
    NSFileWrapper *wrapper = [[[NSFileWrapper alloc] initDirectoryWithFileWrappers:nil] autorelease];
    [wrapper addRegularFileWithContents:[@"please work" dataUsingEncoding:NSUTF8StringEncoding] preferredFilename:@"foobar"];
    NSDictionary *metadata = [NSDictionary dictionaryWithObject:@"0.1" forKey:@"Version"];
    NSString* errorDescription = nil;
    NSData* dictionaryData = [NSPropertyListSerialization dataFromPropertyList:metadata format:NSPropertyListBinaryFormat_v1_0 errorDescription:&errorDescription];
    if(!dictionaryData)
    {
        if(!errorDescription)
            errorDescription = @"Unknown error";
        if(outError)
            *outError = [NSError errorWithDomain:@"YourErrorDomain" code:69 userInfo:[NSDictionary dictionaryWithObject:errorDescription forKey:NSLocalizedDescriptionKey]];
        return nil;
    }
    [wrapper addRegularFileWithContents:dictionaryData preferredFilename:@"Info.plist"];
    return wrapper;
}