[Magritte] MAToOneRelationDescription explanation

[John McKeon]

Hello German,

On Sun, Jan 31, 2010 at 8:42 AM, Germán Arduino <garduino at gmail.com> wrote:

> Hi:
>
> I'm a bit confused using relationships between objects in Magritte.
> Let's start with MAToOneRelationDescription.
>
> I've a Contracts system were each contract have 1:1 Relation with
> Suppliers (another collection of the system), then on the form
> to add contracts, on the place of Supplier I wants to show a combo
> with, for example, all the suppliers names loaded on the
> suppliers collection, to select one to use in the current contract.
> Very common need I think (Is the way I used to do with Mewa).
>
> But trying with different options (not found much doc about each
> possible method to use on MAToOneRelationDescription) I get
> a "create" button than, certainly, is not what I need and really not
> understand the fundamentals of this button on a single 1:1
> relationship.
>
> On the class side of MAToOneRelationDescription the defaultComponentClasses
method returns an array with two component classes:
MAExternalEditorComponent and MAInternalEditorComponent. By default, the
first of these is what you are seeing rendered. To override this behavior
you have to send componentClass: to your description. Magritte does not come
with a select list component for the MAToOneRelationDescription but it is
easy to create one descended from MAOneToOneComponent that will render a
select list of all the instances of the classes declared in the classes:
message sent to the description. So your descriptionSupplier method might
look like:

^MAToOneRelationDescription new
   classes: (Array with: Supplier);
   componentClass: NewSelectionComponent;
   accessor: #supplier;
   &etc

I threw one together and attached the FileOut of it. It is descended from
the ExternalEditor component so it renders a Create button as well.

One caveat, I am using Seaside 2.8

Hope this helps
John


> Any clarification about this topic, examples, documentation, etc will
> be greatly appreciated.
>
> BTW, I'm using Seaside 3.0 with installed on Pharo rc2 with the
> Configuration provided by Dale.
>
> Cheers.
> --
> =================================================
> Germán S. Arduino  <gsa @ arsol.net>   Twitter: garduino
> Arduino Software & Web Hosting   http://www.arduinosoftware.com
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> =================================================
>
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