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Re: Pass-through bindings from parent to child component
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Re: Pass-through bindings from parent to child component


  • Subject: Re: Pass-through bindings from parent to child component
  • From: Chuck Hill <email@hidden>
  • Date: Sun, 6 Jan 2008 20:57:12 -0800

Hi Paul,

On Jan 6, 2008, at 8:41 PM, Paul Hoadley wrote:

I know there's at least one other recent thread about component bindings, but can anyone give me a start on this:

On 03/01/2008, at 4:18 PM, Paul Hoadley wrote:

Is there an idiom for passing through _any and all_ bindings from a parent to a child component without being specific about it?

Simply put, no. The is reason is that parents do not pass bindings to their children. The children take them from their parents. If the child was not written to handle arbitrary bindings, there is no way you can force it to. You could subclass the child and extend it to handle any and all bindings.



That is, I've got a component that wraps a Dynamic Element. If I add the binding 'abc="xyz"' to, say, a WOTextField, it will pass that through to the HTML 'input' element as an attribute and its value.

It does not pass them through to WOTextField. WOTextField (or one of its superclasses, WOInput or WOHTMLElement, I don't recall and am too lazy to figure it out) has code to take any bindings that it does not recognize and add them to the input as key=value.



How can I get my containing component to do something similar—is there an idiom for passing completely arbitrary bindings from a parent to a child component? If I can work that out, I think I can answer my original questions:

1. I want to be able to set any bindings on the WOBrowser which were set on the LSBrowser. I can list them out in the WOD:

browser : WOBrowser {
	list = ^list;
	item = ^item;
	selections = ^selections;
	displayString = ^displayString;
	multiple = ^multiple;
	id = ^id;
	value = ^value;
	escapeHTML = ^escapeHTML;
	selectedValues = ^selectedValues;
	name = ^name;
	disabled = ^disabled;
	size = ^size;
	class = classList;
}

But then WOLips flags an error because I've "set" 'selectedValues' and 'selections'. All I'm trying to express here is that whichever of the two is set on the parent should be passed through to the child.

I think that what you need to do is to implement LSBrowser as a WODynamicElement so that you have the necessary access to the bindings. This means that instead of using a WOBrowser, you are going to have to re-implement it. Subclassing WOBrowser might be a good approach.



2. Similarly, I'd like to be able to pass through arbitrary bindings such as 'id' in the list above without having to be specific about it. Although 'id', for example, is not in the API for WOBrowser, WOBrowser will pass that through to the corresponding HTML element. How can I mimic this functionality in my LSBrowser?

When you need "advanced" access to bindings like this, WODynamicElement is usually the best solution. This is a small amount of information on them here: http://wiki.objectstyle.org/ confluence/display/WO/Web+Applications-Development-WO+Component-Code +Template+and+WODs


Otherwise, feel free to ask questions and I will try to help you out.


Chuck

--

Practical WebObjects - for developers who want to increase their overall knowledge of WebObjects or who are trying to solve specific problems.
http://www.global-village.net/products/practical_webobjects






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