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Re: Nested component communication
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Re: Nested component communication


  • Subject: Re: Nested component communication
  • From: Zak Burke <email@hidden>
  • Date: Wed, 11 Aug 2004 14:58:06 -0400

David,

I confess I haven't investigated the subtleties of WOComponent parameter passing.

Using the same technique I mentioned origianlly, I have built deeply nested structures where, for example, the items contained in a WORepetition are themselves components.

The component will have code like this:

	<WEBOBJECT NAME=foRepetition>
		<WEBOBJECT NAME=foItemTemplate></WEBOBJECT>
	</WEBOBJECT>

	====
	foRepetition: WORepetition {
		item = foItem;
		list = foList;
	}

	foItemTemplate: ItemSummary {
		fo = foItem;
	}


And the subcomponent will have an instance variable named "fo".

This is essentially the reverse of what I initially described: instead of a component passing a value up to a wrapper, this is a component passing a value down to a sub-component. If that's what you're trying to do, then I'm really stumped, because the technique works for me.

To debug the problem, try stashing NSLog.out.println statements in the WO magic methods (the constructor, awake, appendToResponse) to see if the object is being set and overwritten or if it's never being set.

As to whether the nested component's variables are public or private, it shouldn't technically matter, although private variables with get/set methods are superior from an OO point of view, and WO will find "setKey" and "getKey" automatically when you try to set "key" from a separate component or from a web form.

zak.



David Holt wrote on 8/11/04 12:25 PM:

Thanks Zak,

Your response makes me think that I should clarify my problem a little better.

Variables pass from the component content to the Wrapper component perfectly. I am using a pageTitle dynamically generated from the componentContent binding.

My problem seems to be how to pass the variable from the componentContent to its nested navigation bar and from the navigation bar to its nested menu elements. Should I be using setter methods explicitly? I think that the variable value is passing, but then is it possible it is getting reset during the response loop? There is an example in the old WebObjects Developer's Guide for version WO4.5 that shows a parent component synchronizing to a child, and a child synchronizing to the parent. The book says (on page 148): "For instance, it's sufficient in the example shown in Figure 35 to simply declare a childValue instance variable in the child component and a parentValue instance variable in the parent." on the following page it says: "Component synchronization can sometimes lead to values being set when you don't want time to be set. You have no control over when, or how often a value is passed to and from the parent."

Is there a better way for a nested element to know where it is (i.e. which page level component is displaying it) and base its behaviour on where it is?

On 11 Aug 2004, at 5:44 AM, Zak Burke wrote:

David,

Yeah, I've had a hard time tracking down details about inter-component communication. Here's what works for me: In the api file of the component which is being wrapped, you can directly set the wrapper's variables like this:

WebObjectTagName: WrapperComponent {
    var1 = "static string value";
    var2 = aMethodValue;
}

This assumes that:
* the class WrapperComponent has variables var1 and var2. set-methods
  probably work too, but I haven't tried
* the inner component's class has a method aMethodValue()
* var2 and the value returned by aMethodValue() are the same type

In your case, it sounds like you should be able to set the wrapper class's "tabOne" variable from the wrapped pages, just like setting var1 in the example above.

Good luck --

zak.


David Holt wrote on 8/10/04 6:52 PM:

Hello,
I am trying to get a navigation bar to work so that an image changes when the user is on the page (like the tabs on Apple's site).
The way I have set it up is to have a page wrapper containing a WOComponentContent and a NavigationBar Component made up of Rollover components. In my API for the wrapper I have set a boolean variable called "tabOne" and for all of the components that fill the "WOComponentContent" under "tabOne" I have set their "tabOne" binding to "true".
I have also placed "tabOne" variables in the wrapper component, the NavigationBar component and the Rollover component. I have wrapped the rollover button for tabOne in a conditional to display the rollover when the boolean is false (i.e. not on a page that is in tabOne) and a static image when the boolean is true. My problem is that the boolean is always evaluating to false on pages where "tabOne" is true and as a result only the rollover is displayed in its conditional. From my reading, it seems that the component communication is automatic from the parent components to child components so long as the variables are named the same thing.
Am I misunderstanding something about how the communication would occur from ComponentContent>Wrapper>NavigationBar>Rollover ? If so, what would be a better way to implement this? Thanks,
David
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References: 
 >Nested component communication (From: David Holt <email@hidden>)
 >Re: Nested component communication (From: Zak Burke <email@hidden>)
 >Re: Nested component communication (From: David Holt <email@hidden>)

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