Acts_as_tree

My goal is to use nested

    elements to display a hierarchical view
    of an entire table. It is my understanding that all acts_as_tree does
    is make available 3 additional methods: ‘ancestors’, ‘root’, and
    ‘siblings’. As useful as these methods may be, I don’t see how they
    are going to help me achieve my goal. It seems to me that I’m
    additionally going to need to somehow get the table sorted properly;
    and, even after I have done that I’m still left with the difficult
    issue of keeping track of levels and opening and closing
      tags
      appropriately. Am I missing something?

      Thanks for any input.

      ... doug

Doug J. wrote:

My goal is to use nested

    elements to display a hierarchical view
    of an entire table. It is my understanding that all acts_as_tree does
    is make available 3 additional methods: ‘ancestors’, ‘root’, and
    ‘siblings’. As useful as these methods may be, I don’t see how they
    are going to help me achieve my goal. It seems to me that I’m
    additionally going to need to somehow get the table sorted properly;
    and, even after I have done that I’m still left with the difficult
    issue of keeping track of levels and opening and closing
      tags
      appropriately. Am I missing something?

      Thanks for any input.

      ... doug

Doug,

use siblings() to iterate through the node’s children and put a

  • for
    each, if the child itself has children then wash and repeat… think
    helper functions and recursion…

    ilan

  • Ilan B. wrote:
    […]

    use siblings() to iterate through the node’s children and put a

  • for
    each, if the child itself has children then wash and repeat… think
    helper functions and recursion…
  • That’s pretty inefficient on a tree of any size, at least if you’re
    doing a DB query each time instead of loading the whole tree into
    memory.

    Instead, use awesome_nested_set or similar. It provides a data
    structure much better suited to what you want.

    ilan

    Best,

    Marnen Laibow-Koser
    http://www.marnen.org
    [email protected]

    use siblings() to iterate through the node’s children and put a

  • for
    each, if the child itself has children then wash and repeat… think
    helper functions and recursion…
  • Thanks to both contributors for the input.

    This is not a homework assignment. It represents an actual need; but,
    I would like to treat it as a learning experience. The tree involved
    is going to be pretty small, I’m guessing typically 10 - 20 nodes. I
    think my best approach would be to begin with acts_as_tree; and, when,
    as, and if I ever get that working then try advancing to a nested set
    approach. (Pro Active Record says that nested sets can be “a little
    complex to grasp and manage”. That scares me at my level of
    understanding.)

    Having said that, please allow me to clarify the suggested
    acts_as_tree approach.

    use siblings() to iterate through the node’s children

    By “the nodes children” I think that you mean the children of each of
    the root nodes. Am I correct?

    put a

  • for each child, if the child itself has children then wash and repeat
  • Translation: For each child of a given root node:
    if that child has no children put an

  • for
    that child.
    Else put a
      and begin processing the
      grandchildren

      I think that I get the concept. I’m going to give it a whirl. I will
      likely have additional questions. However, it could be days before I
      discover them. :slight_smile:

             ... doug
  • Marnen Laibow-Koser wrote:

    That’s pretty inefficient on a tree of any size, at least if you’re
    doing a DB query each time instead of loading the whole tree into
    memory.

    Very true! However, if only a couple of branches will be opened for a
    given tree and the branches will be opened via an AJAX call then the
    performance will most likely be better than retrieving the whole tree
    into memory initially and then trucking it across the wire… depends
    upon the situation I guess…

    Anyways, question smelled like a homework assignment so I didn’t reason
    on performance…

    ilan

    Doug J. wrote:

    This is not a homework assignment. It represents an actual need; but,
    I would like to treat it as a learning experience. The tree involved
    is going to be pretty small, I’m guessing typically 10 - 20 nodes. I
    think my best approach would be to begin with acts_as_tree; and, when,
    as, and if I ever get that working then try advancing to a nested set
    approach. (Pro Active Record says that nested sets can be “a little
    complex to grasp and manage”. That scares me at my level of
    understanding.)

    Doug,

    Then I would use what Marmen suggested: awesome_nested_set as while the
    earlier approach is probably easier to implement, it is not efficient.
    I mistakenly assumed that it was a homework assignment (as we get a lot
    of questions on this list for that) and was just giving you the “get it
    done” approach

    ilan

    Doug J. wrote:

    (Pro Active Record says that nested sets can be “a little
    complex to grasp and manage”. That scares me at my level of
    understanding.)

    Perhaps they can be, but awesome_nested_set encapsulates the complexity.
    And they’re not really that complex to begin with. Have you read about
    the nested-set data structure?

    Best,

    Marnen Laibow-Koser
    http://www.marnen.org
    [email protected]

    Doug J. wrote:

    �Have you read about the nested-set data structure?

    Yes; but, not in detail. The section on nested sets immediately
    follows the section on acts_as_tree in “Pro-Active Record”.

    I’ve never heard of Pro-Active Record, and it sounds very much like it
    is steering you wrong.

    I take it that awesome_nested_set is not the same thing as
    acts_as_nested_set?

    They are different plugins. When I did my research a few months ago,
    awesome_nested_set seemed the better choice.

    In any event, here’s the deal. I just stumbled onto acts_as_tree a
    few days ago. Before that, I was oblivious to it. Because I was off
    in oblivion, I hardcoded a solution for creating the hierarchical
    view. (It took me about 2 weeks! :slight_smile: ) It uses a linked-records
    approach where each record has a pointer to its ancestor much like
    acts_as_tree.

    Yes, the classic adjacency list structure.

    Surprisingly, it seems to work just fine; however, the
    code is about 100 lines in length and its messy. I’m sure that my
    code is even less efficient than act_as_tree; and, as I say, it seems
    to work just fine. So, I don’t think that performance is going to be
    an issue. I’d like to clean up my messy code.

    OK.

    I think that if I use
    acts_as_tree, I can use my existing database. I just have to be sure
    to declare my foreign key since I named my pointer column ‘parent’
    rather than the default, ‘parent_id’. If I use a nested-set approach,
    I would have to modify/re-create the database.

    You would need to make a very small change (add two numeric fields and
    run one or two simple statements in the migration). It’s quite easy.

    In addition, based on
    Ilan’s comments, I have a vague idea of how to proceed with
    acts_as_tree where I am much more in the dark with nested sets.

    Then learn about nested sets. The principle is not difficult, and the
    data structure works much better. Joe Celko’s articles are a good place
    to start.

    All
    in all and despite your undoubtedly good advice to the contrary, I
    would like to proceed with a acts_as_tree solution.

    It’s your decision, but be aware that based on what you’ve posted,
    you’re basing your decision on the wrong criteria.

    That doesn’t
    mean that I won’t re-do it with nested sets at some future date. I
    just want to make sure that I can walk before I try flying.

    It doesn’t work like that here. It’s more like trying to walk from New
    York to Boston because learning to drive a car seems too hard.

    I hope
    that you guys will stick with me through my adventure which I’m not
    even going to be able to begin for a couple of days because of other
    things which have arisen.

    Thanks ever so much for your awesome help.

    You’re most welcome. Again, please choose a data structure that
    actually suits your needs, not one that looks simpler but won’t do the
    job.

            ... doug
    

    Best,

    Marnen Laibow-Koser
    http://www.marnen.org
    [email protected]

    Have you read about the nested-set data structure?

    Yes; but, not in detail. The section on nested sets immediately
    follows the section on acts_as_tree in “Pro-Active Record”.

    I take it that awesome_nested_set is not the same thing as
    acts_as_nested_set?

    In any event, here’s the deal. I just stumbled onto acts_as_tree a
    few days ago. Before that, I was oblivious to it. Because I was off
    in oblivion, I hardcoded a solution for creating the hierarchical
    view. (It took me about 2 weeks! :slight_smile: ) It uses a linked-records
    approach where each record has a pointer to its ancestor much like
    acts_as_tree. Surprisingly, it seems to work just fine; however, the
    code is about 100 lines in length and its messy. I’m sure that my
    code is even less efficient than act_as_tree; and, as I say, it seems
    to work just fine. So, I don’t think that performance is going to be
    an issue. I’d like to clean up my messy code. I think that if I use
    acts_as_tree, I can use my existing database. I just have to be sure
    to declare my foreign key since I named my pointer column ‘parent’
    rather than the default, ‘parent_id’. If I use a nested-set approach,
    I would have to modify/re-create the database. In addition, based on
    Ilan’s comments, I have a vague idea of how to proceed with
    acts_as_tree where I am much more in the dark with nested sets. All
    in all and despite your undoubtedly good advice to the contrary, I
    would like to proceed with a acts_as_tree solution. That doesn’t
    mean that I won’t re-do it with nested sets at some future date. I
    just want to make sure that I can walk before I try flying. I hope
    that you guys will stick with me through my adventure which I’m not
    even going to be able to begin for a couple of days because of other
    things which have arisen.

    Thanks ever so much for your awesome help.

            ... doug

    Thanks, Marmen. I will give your undoubtedly good advice serious
    consideration. As I said, I’m going to have to take a break from this
    project for a couple of days anyway in order to tend to some other
    things that have arisen. Thanks again.

         ... doug

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