Quick Question about Magritte

[Lukas Renggli]

> Ok, this seems to work, slight modification from yours to prevent  
> the cascade accessor from being added more than once, otherwise  
> every render built up long chains of cascading accessors, does this  
> seem right?  Also, any way to add a label or something to each  
> group of fields?

Aha, I see the problem. Sorry, I didn't think that far in my first  
example. It would be probably easier to copy the descriptions before  
modifying them:

orderView := (anOrder description ***copy***
     addAll: (anOrder billingAddress description collect: [ :each |
         each ***copy*** accessor: (MACascadeAccessor
             accessor: (MASelectorAccessor selector: #billingAddress)
             next: each accessor) ]);
     addAll: (anOrder shippingAddress description collect: [ :each |
         each ***copy*** accessor: (MACascadeAccessor
             accessor: (MASelectorAccessor selector: #shippingAddress)
             next: each accessor) ]);
     asComponentOn: anOrder) addValidatedForm: #(#update #cancel ).

I see that this is commonly used pattern, in fact I am using such  
code quite a lot in our web-applications. I see two possibilities to  
make this easier:

1. Introduce a method in MAContainer doing exactly what we saw above:

     (anOrder description
         flatten: (MASelectorAccessor selector: #billingAddress))
         flatten: (MASelectorAccessor selector: #shippingAddress)
         ...

2. Introduce a special description doing the same:

     Order>>descriptionBillingAddress
         ^ (MAComposedDescription selector: #billingAddress)
             reference: Address description;
             yourself.

     Order>>descriptionShippingAddress
         ^ (MAComposedDescription selector: #shippingAddress)
             reference: Address description;
             yourself.

The first approach can lead to _duplicated_ code and tends to _waste_  
memory. The problem with the second approach is that you have those  
referenced objects _always_ in the description of Order, maybe you  
don't want this. Probably we need both?

Any thoughts?

Lukas

-- 
Lukas Renggli
http://www.lukas-renggli.ch