In Defense of Copy and Paste

Re:In Defense of Copy and Paste by drostie on Friday February 08, 2013 @02:05PM (#5189529)

I believe they intended the 'proper' code to look like:

    def global_feed(request):
        tweets = Tweet.objects.all()
        tweets = itertools.ifilter(lambda t: not t.is_profane(), tweets)
        return render(request, 'global_feed.html', {'tweets': tweets})

    tweets_per_page = 20
    def user_timeline(request, username):
        tweets = Tweet.objects.filter(user__username=username)
        page = request.GET.get('page', 1)
        offset = (page - 1) * tweets_per_page
        tweets = tweets[offset:offset + tweets_per_page]
        return render(request, 'user_timeline.html', {'tweets': tweets})

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Re:In Defense of Copy and Paste by danso on Friday February 08, 2013 @02:27PM (#5189636)

So the problem with that is seems to be...what if there was another view that required pagination?

So the two unpleasant scenarios seem to be this:

1) The OP's assertion that DRYing the code may unintentionally break functionality in all the places that use it.

2) The DRY assertion: copy-pasting functionality, such as pagination, makes it more likely that the pagination functionality won't be properly updated across all the modules that use it.

I guess it's a case of YMMV...because in this hypothetical app, it doesn't seem likely that the number of views will multiply, thus making it easier to update the copy-pasted code. But that seems like a mindset as prone to future problems than one that is more DRY-minded.

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