Factory method pattern: Difference between revisions

Revision as of 19:29, 11 December 2003

Revision as of 19:31, 11 December 2003

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1 - A bad way to design the ImageReader

This [[method]] has the [[advantage]] of abstracting the [[file type]] from the [[class]] that calls this ImageReader, but as the number of file types supported gets larger, the code will quickly become huge, unwieldy and hard to maintain.

Another [[solution]] that seems possible is to have a separate [[object]] for each of these file types:

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Again, there are [[advantage]]s to this [[method]] (clean [[organisation]] of the ImageReader classes, split up in several classes), but this is at the [[cost]] of the [[abstraction]] of the image type. Again, when you get to have dozens of file types, this will be unsatisfactory and produce code that is hard to maintain.

So what's the [[solution]]? Simply to take the best of both worlds, by using the Factory pattern (which you should already have an idea of by now). The [[Factory]] is a [[class]] that returns another class depending on the [[context]]. So in this [[situation]], keeping the separate [[class design]] as in the last example:

public class ImageReaderFactory