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Re: <tree-node> in DUIM

oodl@my-deja.com writes:

> The <tree-node> class is listed in the DUIM documentation as being
> an "Open abstract instantiable class".  I should be able to call
> make on it, right?

I'm not sure about this as I've never created a <tree-node>. Perhaps
the documentation is just wrong.

> I am not sure how to populate a <tree-control> with children so I
> would appreciate having an example showing how to populate the
> control with pre-existing children, not only with children generated
> from a method like this: method (x) vector(x * 2, 1 + (x * 2)) end
> as they do in the sample code.

Here is an example cut from a program I did. I don't know if it is the
best way but it's the way I did it as a <tree-control> newbie. The
programs displays details on horse races and results in a race
meeting. The tree control displays something like:

- Meeting
|--- + Race 1
|--- + Race 2
|--- - Race 3
|----|--- + Horse 1
     |--- + Horse 2
     |--- + Horse 3
     |--- - Horse 4
     |-------- Various Horse details

These are all existing classes modelled like:

define class <meeting> (<object>)
  slot meeting-races;
end;

define class <race> (<object>)
  slot race-horses;
end;

define class <horse> (<object>)
  slot horse-details;
end;

The classes are populated from database queries in a lazy manner
(ie. They are virtual slots, making the queries if the results have
not been retrieved yet).

The table-control was created as:

  make(<tree-control>,
    roots: all-meetings,
    label-key: race-view-label-generator,
    children-generator: race-view-child-generator);

all-meetings contains a list of <meeting> classes.

There were methods specialised on the different types:

  define method race-view-child-generator(object :: <object>)
    #[]
  end method race-view-child-generator;

  define method race-view-child-generator(meeting :: <meeting>)
    sort(meeting.meeting-races, 
          test: method(a, b)
            a.race-track < b.race-track 
          end method;
  end;

  define method race-view-child-generator(r :: <race>)
    r.race-horses
  end;

  define method race-view-child-generator(h :: <horse>)
    h.horse-details;
  end;

  define method race-view-child-generator(hd :: <horse-details>)
    #[];
  end;

  define method race-view-label-generator(s :: <string>)
    s
  end method race-view-label-generator;

  define method race-view-label-generator(m :: <meeting>)
    format-to-string("%s - %s", m.meeting-date, m.meeting-title)
  end method race-view-label-generator;

  define method race-view-label-generator(r :: <race>)
    // Extract and return race name
  end method race-view-label-generator;

  define method race-view-label-generator(h :: <horse>)
    // Extract and return horse name
  end method race-view-label-generator;

  define method race-view-label-generator(hd :: <horse-details>)
    // Extract and return horse details name
  end method race-view-label-generator;

Typed from memory and it's been a while since I've used <tree-control>
but hopefully you get the idea.

Chris.
-- 
http://www.double.co.nz/dylan
References: