Instance Method

provideThumbnailForFileRequest:completionHandler:

Creates a thumbnail of a custom file type for a specific request.

Declaration

- (void)provideThumbnailForFileRequest:(QLFileThumbnailRequest *)request completionHandler:(void (^)(QLThumbnailReply *reply, NSError *error))handler;

Parameters

request

The request that contains information about the thumbnail that you need to provide, such as the URL to the file.

handler

The completion handler to call when you finish creating a thumbnail. Call the completion handler with a QLThumbnailReply if you can provide a thumbnail or with an NSError if you can’t create a thumbnail.

The platform doesn’t draw a thumbnail if you pass an error to the handler or the reply is nil.

You can call the handler asynchronously after the method has returned.

reply

The object containing information about the thumbnail image that the platform uses to draw the thumbnail.

error

An error object that indicates why the thumbnail generation failed, or nil if the thumbnail generation succeeded.

Discussion

To provide a thumbnail for a custom file type, subclass QLThumbnailProvider, implement this method, and return a QLThumbnailReply that either contains a drawing block or the URL to an image file.