Inside Macintosh: Cyberdog Programmer's Kit / Part 3 - Cyberdog Reference

Chapter 7 - Classes and Methods

CyberDownloadExtension

Superclasses

CyberExtension --> ODExtension --> ODRefCntObject --> ODObject

Subclasses

none

The CyberDownloadExtension class defines extra behaviors for a part that is to be used as a download part.

Description

The CyberDownloadExtension class is an extension that allows a part to be used as a download part, which downloads content referenced by a Cyberdog item to disk. A Cyberdog download part has two extensions: a CyberDownloadExtension subclass extension and a CyberPartExtension subclass extension.

CyberDownloadExtension is an abstract superclass that you must subclass and implement to create your own customized download part. Cyberdog provides a fully implemented download part; to use this download part, you do not need to subclass this class.

The download part is used in several situations, such as the following:

• When the user drags a Cyberdog item from a display part (a Gopher display part, for example) and drops it in the Finder. In this case, the display part can create a download part and call its CyberDownloadExtension methods to download to disk the data referenced by the Cyberdog item. Optionally, the download part can display progress using its own window.
• When the user opens a Cyberdog item (by clicking on an HTML link, for example). In this case, if the Cyberdog item cannot find a Cyberdog display part editor to bind to, the Cyberdog item can create a download part and call the download part's OpenCyberItem method. The download part downloads the data to disk, obtains an opener part, and calls the opener part's OpenFile method to open the file created during the download. The download part displays progress in the opener part.
• When the user selects several Cyberdog items and then chooses the Get Items from Server command from either the Gopher or FTP menu. In this case, Cyberdog creates a single download part to download and save to disk the content referenced by all the selected Cyberdog items.

The CyberDownloadExtension interface provides two different methods for queuing requests to download the content referenced by a Cyberdog item and save it to a file: DownloadCyberItem and PostDownloadRequest. Both methods add a request to download data to the download part's queue. You initiate pending download requests by calling StartDownloads.

The DownloadCyberItem method is the simplest method to use; when you call it, you pass the Cyberdog item and the specification of the destination file. The PostDownloadRequest method allows you to register a function that Cyberdog can call to notify you when the download is complete. In addition, the PostDownloadRequest method allows you to specify whether you want the downloaded file to be decompressed before it is saved.

The download part requests and uses a Cyberdog item's associated stream to download the Cyberdog item. When the download part is finished processing its download requests, it destroys itself.

Methods

This section presents summary descriptions of the CyberDownloadExtension methods grouped according to purpose, followed by detailed descriptions.

Requesting a Download

CancelRequest

Cancels a request to download data to disk.

DownloadCyberItem

Requests the download of data referenced by a Cyberdog item to disk.

PostDownloadRequest

Requests the download of data referenced by Cyberdog item to disk and registers a completion notification function.

Initiating a Download Request

StartDownloads

Initiates the download requests queued for a download part.

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Methods

CancelRequest

DownloadCyberItem

PostDownloadRequest

StartDownloads