On Jun 5, 2007, at 5:24 PM, Ariel Jakobovits wrote:
> I am learning about Cairgorm, and about the usage of Value Objects.
> This makes sense. However, I am curious about how to handle basic
> operations on these value objects.
I just went through the exact same learning curve.
I'm not an authority by any means, but what I did was:
1. Create a new command called "UpdateAssetCommand", or in your case
"UpdateItemCommand"
2. Pass in through the cairngorm event the updated properties on your
item.
3. Your UpdateItemCommand will then execute the appropriate update by
grabbing the item from the Model, iterating over the properties and
changing them. In my case, I have an ArrayCollection of VOs and just
iterated over that collection until I got the asset in question and
then updated its properties.
> When I pass an item to a form component, I am inclined to permit
> the form component to perform update operations on the item like
> item.assignToCategory(category); I think this is intuitive for the
> design of the form component.
Just a side note : are you passing this item to the form component
explicitly, or is it bound to the model – ie, data ==
{model.selectedItem}. Binding to the model is much preferred.
Additionally, it shouldn't be against the grain to extend your item
VO with a method to update it's properties based on a passed in
Object, Array(Collection) or XMLList if you don't want to deal with
assigning a bunch of properties by name in the Command. But you'd
still do the actual updating in the command itself. I wouldn't do it
in the form.
> But this means that the item value object is not just a model, but
> also a controller in some aspect. The alternative as I understand
> it is to say something like Controller.addCategoryToItem
> (item,category) which is OK but I think it is sort of clunky.
>
> Direction? Advice? Am I missing something? Please.
I don't think you need to get that explicit with your commands.
Commands should be generic enough (ie, updateItem) to reuse in
different cases.
good luck with that,
jon
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