Just how would you make it lazy??
My scenario: a domain-driven approach to web development. I have several
domain classes, such as Client, Phone, Address, etc. For example, the
Client class would have something like this:
Client.java
-> String firstName
-> String lastName
-> List<Phone> phones
-> Address address
etc
I then go and create a FormClient.html Tapestry component with something
like this:
<span jwcid="@FieldLabel" displayName="First Name" /><span
jwcid="@TextField" value="ognl:value.firstName" />
<span jwcid="@FieldLabel" displayName="Last Name" /><span
jwcid="@TextField" value="ognl:value.lastName" />
<span jwcid="@For" source="ognl:value.phones" value="ognl:phone">
<span jwcid="@forms/FormPhone" value="ognl:phone" />
</span>
<span jwcid="@forms/FormAddress" value="ognl:value.address" />
etc...
As you see, I'm binding the subcomponents (FormPhone, FormAddress) with
the Client object directly. Then on rewind I have to do nothing: the
address is automatically assigned to value.address and so forth (the
list of phones is a special case, but similar).
Now, the graph can get pretty complex, so I initialize every FormXXX
component's value (in case it's null) in pageBeginRender. But, for this
to work, the parent component must be already initialized, because, if I
try to do a setValue() on "value.address", it throws an NPE when and
value is null (since the parent hasn't been initialized yet).
Summary: It's just a case of component composition. It's like using
constructors. The object's fields constructors are called after the
parent one.
It's intuitive to assume events are fired in order [parent -> child]. At
least it took me a while to figure out what was going wrong.
--
Ing. Leonardo Quijano Vincenzi
Director Técnico
DTQ Software
Ron Piterman wrote:
I Usually avoid this kind of initialization by making it happen lazy,
If you would share the scenario... maybe there is a nice solution...
Cheers,
Ron
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