Is Possible to Set a Widget Constraint Dynamically? - grails-2.0

Question

I'm designing dynamic forms for grails and I was wondering if it was at possible to set the widget constraint dynamically?

Answer 1

Setting the widget constraint is not the way to attack this. I suppose the simplest method would be to choose the tag you'd like to display based upon some condition using an "if" tag in your view or template. For instance:
Say you have a Book
class Book {
String name
}
If you use Grails generate-view for this class, Grails will produce a template called _form that looks like the following:
<div class="fieldcontain ${hasErrors(bean: bookInstance, field: 'name', 'error')} ">
<label for="name">
<g:message code="book.name.label" default="Name" />
</label>
<g:textField name="name" value="${bookInstance?.name}"/>
</div>
You can test your condition in this form and change the view:
<div class="fieldcontain ${hasErrors(bean: bookInstance, field: 'name', 'error')} ">
<label for="name">
<g:message code="book.name.label" default="Name" />
</label>
<g:if test="$yourCondition">
<g:textField name="name" value="${bookInstance?.name}"/>
</g:if>
<g:else>
<g:textArea name="name" value="${bookInstance?.name}"/>
</g:else>
</div>
Now the view will display a textField or textArea field based upon $yourCondition.