Which is considered the best method in this example ?

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  • d d
    #1

    Which is considered the best method in this example ?

    I have a large object with many sub-objects. They may go down 4 or 5
    levels and I'm not sure how best to code a method that does operations
    on that data. Here's an attempt to make it an isolated example:

    var level1={
    info:"abc", //lots of other properties here alongside info
    level2:{
    moreinfo:"def", //lots of properties at this level too
    level3:[ //array of level 3 objects
    { path:"imagepath ",width:123,hei ght:456,
    getImgTag:funct ion(){} //return the tag string on demand
    },
    { }] //various other level 3 objects
    },
    someotherbigobj satlevel2:{.... }
    }

    This would be called with:

    mytag = level1.level2.l evel3[0].getImgTag();

    Inside the getImgTag method, the 'this' property is the level3 object in
    the array. It's not the level1 object. This is good from one side, it
    means I can access this.path, this.width etc.

    On the downside, it means I don't have access to data outside that
    object (e.g. the moreinfo string (which has the value "def"), or the
    info string even further out (which has the value "abc"). I also don't
    know which level3 element I am in the array. This can lead to me needing
    to potentially duplicate data.

    When I'm generating the img tag, I want to give it an id. I want that id
    to be made up of data from level1, level2 and the array index. In this
    example, I would want the id to be "abc_def_0" . For the image tag for
    level3 array element 2, I'd want it to be "abc_def_2" .

    This means I either need to pass in the info and moreinfo and array
    index in the call to getImgTag (this is ugly), or I pass in the whole
    object itself and do something like this:

    getImgTag:funct ion(mainobj,arr ayidx){
    var id=mainobj.info +"_"+mainobj.le vel2.moreinfo+" _"+arrayidx;
    ....
    }

    Somehow this is all not coming together as nicely as I'd hoped :(

    Now I can duplicate this info and moreinfo and the array index itself
    all into the level3 object but that leads to duplication of data that is
    common to all of the level3 objects (and therefore has an argument to be
    outside of it). I remember from my OO courses back in the early 90's
    that an object should have all the information itself about what it
    needs to do, but it's leading to an inefficiency. Would I really want to
    do this:

    var level1={
    info:"abc", //lots of other properties here alongside info
    level2:{
    moreinfo:"def", //lots of properties at this level too
    level3:[ //array of level 3 objects
    { path:"imagepath ",width:123,hei ght:456,
    iamindex:0,
    level1info:"abc ",
    level2info:"def ",
    getImgTag:funct ion(){} //return the tag string on demand
    },
    { }] //various other level 3 objects
    },
    someotherbigobj satlevel2:{.... }
    }

    If the info and moreinfo were only used by these level3 image objects,
    then it wouldn't be so bad, but there are so many other object types at
    different levels that also need that info. It might end up getting
    duplicated dozens of times.

    Am I missing the obvious solution? It is monday morning, it's quite
    possible.

    ~dd
    Tags: None
    • d d
      #2
      Re: Which is considered the best method in this example ?

      d d wrote:
      Am I missing the obvious solution? It is monday morning, it's quite
      possible.
      Well, it seems like I was missing the obvious. I moved my method to the
      root of the object, and pass in only one param - the array index.

      var level1={
      info:"abc", //lots of other properties here alongside info
      level2:{
      moreinfo:"def", //lots of properties at this level too
      level3:[ //array of level 3 objects
      { path:"imagepath ",width:123,hei ght:456 },
      { }] //various other level 3 objects
      },
      getImgTag:funct ion(idx){
      //I have access to info, moreinfo, and the array
      //and can create a ptr to the obj I want to work on
      //from the idx param:
      var obj=this.level2 .level3[idx];
      //use obj.width, obj.height
      } //return the tag string on demand
      }

      If there's a better way, I'd still like to hear about it...

      ~dd

        Comment

        • Peter Michaux
          #3
          Re: Which is considered the best method in this example ?

          On Jul 30, 5:38 am, d d <dd_no_s...@ple ase.netwrote:
          I have a large object with many sub-objects. They may go down 4 or 5
          levels and I'm not sure how best to code a method that does operations
          on that data. Here's an attempt to make it an isolated example:
          >
          var level1={
          info:"abc", //lots of other properties here alongside info
          level2:{
          moreinfo:"def", //lots of properties at this level too
          level3:[ //array of level 3 objects
          { path:"imagepath ",width:123,hei ght:456,
          getImgTag:funct ion(){} //return the tag string on demand
          },
          { }] //various other level 3 objects
          },
          someotherbigobj satlevel2:{.... }
          >
          }
          >
          This would be called with:
          >
          mytag = level1.level2.l evel3[0].getImgTag();
          >
          Inside the getImgTag method, the 'this' property is the level3 object in
          the array. It's not the level1 object. This is good from one side, it
          means I can access this.path, this.width etc.
          >
          On the downside, it means I don't have access to data outside that
          object (e.g. the moreinfo string (which has the value "def"), or the
          info string even further out (which has the value "abc"). I also don't
          know which level3 element I am in the array. This can lead to me needing
          to potentially duplicate data.
          >
          When I'm generating the img tag, I want to give it an id. I want that id
          to be made up of data from level1, level2 and the array index. In this
          example, I would want the id to be "abc_def_0" . For the image tag for
          level3 array element 2, I'd want it to be "abc_def_2" .
          >
          Can you build this big object in phases? Your objects are never sealed
          in JavaScript so you can always modify them in stages.

          var level1 = {
          info:"abc"
          };

          level1.level2 = {
          blah: "dfe"+level1.in fo
          zip: function() {return this.blah + level1.info;}
          };

          Peter

            Comment

            • d d
              #4
              Re: Which is considered the best method in this example ?

              Peter Michaux wrote:
              Can you build this big object in phases? Your objects are never sealed
              in JavaScript so you can always modify them in stages.
              >
              var level1 = {
              info:"abc"
              };
              >
              level1.level2 = {
              blah: "dfe"+level1.in fo
              zip: function() {return this.blah + level1.info;}
              };
              Peter
              I will be building it in phases. The initial object will contain "the
              data" and one line of JS which loads a standard JS file. That standard
              JS file will thten be adding some extra default/constant data and the
              methods to the object.

              I see what you're saying, the data can be easily duplicated while
              building the object. It's still duplication though. I think I'd prefer
              the methods being at the root (having access to the whole object via
              this), and they receive a ptr to the sub-object to work on, or an index
              into an array of sub-objects.

              ~dd

                Comment

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