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

Chapter 7 - Classes and Methods / CyberDownloadExtension

PostDownloadRequest

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

CDDownloadRequestID PostDownloadRequest (in CyberItem item, 
in FSSpecPtr destSpec, 
in ODBoolean decomp, 
in DownloadCompletionUPP completionProc, 
in Ptr completionProcData);

item

The CyberItem object that specifies the data to be downloaded to disk.

destSpec

A pointer to a file specification that specifies the file in which to save the data.

decomp

kODTrue if the download part should attempt to decompress the downloaded data before saving it to the file; otherwise, kODFalse.

completionProc

A pointer to a programmer-defined function that Cyberdog calls when the data has been downloaded to disk.

completionProcData

A pointer to data that is passed to the callback function specified by completionProc.

return value

An ID that uniquely identifies the download request.

DISCUSSION

This method adds a Cyberdog item to this download part's queue. If nil is specified for the destSpec parameter, the download part decides where to save the data. To cancel a download request, you call the CancelRequest method, passing the ID returned by this method.

This method is similar to DownloadCyberItem except that it allows you to control whether the downloaded data is decompressed and to specify a callback function called by Cyberdog when the download operation is complete. The data pointed to by the completionProc parameter is passed to the callback function.

The following type is used for download completion functions. The callback function takes five parameters: an environment parameter, a pointer to a Cyberdog item, an event code that describes the results of the download, a pointer to a file specification, and a pointer to some data.

typedef void (* DownloadCompletionProcPtr) (
Environment* ev,
CyberItem* item,
CDDownloadEvent eventCode,
FSSpec* destFile,
Ptr userDataPtr);

The MyDownloadCompleted programmer-defined function (page 191) illusrates the form of a download completion function.

If you subclass CyberDownloadExtension, you must override this method. Your override must not call its inherited method; that is, your override method must implement this method's functionality completely.

SEE ALSO

The DownloadCyberItem method (page 214).