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Of call-backs and weblog posts

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  • Matt Mower
    Hi Jake, As promised I am posting my message regarding adding an editItem callback to Radio here. *Problem* When a weblog post has been edited, how can an
    Message 1 of 1 , Nov 30, 2002
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      Hi Jake,

      As promised I am posting my message regarding adding an "editItem"
      callback to Radio here.

      *Problem*

      When a weblog post has been edited, how can an application determine
      what has been changed?

      *Motivation*

      Using the weblog API to create & modify posts is currently incompatible
      with liveTopics. Because liveTopics depends heavily upon, among other
      things, the values of adrPost^.flNotOnHomePage and adrPost^.categories,
      when these are edited via the API it may cause the liveTopics database
      to become broken.

      *Context*

      liveTopics manages a Table of Contents (ToC), XFML map & augmented RSS
      feed for each weblog category. Imagine a post is associated with 2
      topics and is a member of 2 categories. That means it will be listed
      under those topics in 2 *distinct* ToC's and up streamed to the
      appropriate category location.

      Now imagine that the post is edited and one of the categories is
      removed. At this point liveTopics must rebuild, for example, the Table
      of Contents for that dropped category since it no longer contains the
      post that was edited and, if this was the only post in that category
      associated with those topics, the topics may disappear too.

      So when a post is edited it is important to liveTopics to know *what has
      changed* as distinct from what the new values are (So for example
      knowing that the post is now in the 'public' category doesn't tell you
      that it used to be in the 'private' and 'project' categories before it
      was edited!)

      This requires that liveTopics be able to ask the question: What
      categories was this post in *before* it got edited?

      To my knowledge there are two likely ways in which a post can be
      modified:

      (1) Via a weblog post form submission
      (2) Using an API e.g. metaweblog

      (1) In this case I can use the afterWeblogPostForm call-back. The
      call-back is received twice for each post: once (the GET call-back)
      before the post is edited and once (the POST call-back) after the post
      is edited. I use the GET call-back to make a copy of the weblog post
      (in system.temp). When the POST call-back is received I can compare the
      copy to the new post and determine whether the values of
      'flNotOnHomePage' and 'categories' have been changed.

      (2) To handle the weblog API I can only hook the postItem call-back.
      However in this case the call-back is received only once, i.e. it gets
      the POST call-back, but not the GET call-back. With no opportunity to
      see the post before it is edited I have no way of knowing what the
      original values of 'flNotOnHomePage' and 'categories' are and, as I
      describe above, the new values are not enough information.

      *Proposal*

      I am proposing a solution that would handle both the situation's I
      describe (and any other similar scenarios in which a post might get
      changed). Essentially what I would like is that UserLand add a new
      call-back:

      editItem( adrPost )

      with the guarantee that it will be called immediately prior to Radio
      modifying the content of a weblog post.

      *Conclusion*

      The addition of an editItem() callback would provide a single seamless
      solution to both scenarios. Code currently in the afterWeblogPostForm
      could be safely moved to editItem and postItem (it doesn't really belong
      in AWPF anyway).

      Regards,

      Matt
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