How to conditionally disable a form input field

Question

Say I have a Domain object Teacher with two fields String name, TeacherType teacherType, where TeacherType is an enum containing AssitantProfessor, AssociateProfessor, Professor.

After I generate the views using grails run-target generate-all Teacher, it produces an _form.gsp that is used for both create and edit of Teacher. In the edit view I want only the name to be editable but the TeacherType to be unmodifiable once created (this is just an example, it is a requirement that certain fields can't be updated after creation). In the create view, both TeacherType and name should be editable.

Since both create.gsp and edit.gsp render the _form template, what is the preferred approach here?

1. Create two separate templates i.e. _formCreate.gsp , _formEdit.gsp; Or
2. Pass in a model map within create.gsp and edit.gsp and use them in _form.gsp to conditionally render the view? e.g.

In create.gsp:

    <fieldset class="form">
        <g:render template="form" model="[teacherInstance: teacherInstance, 'mode':'create']"/>
    </fieldset>

In edit.gsp

    <fieldset class="form">
        <g:render template="form" model="[teacherInstance: teacherInstance, 'mode':'edit']"/>
    </fieldset>

In _form.gsp

    <g:if test="${mode == 'edit'}">
        <g:select name="teacherType" from="${TeacherType?.values()}" keys="${TeacherType.values()*.name()}" required="" value="${teacherInstance?.teacherType?.name()}" disabled="disabled"/>
    </g:if>
    <g:else>
        <g:select name="teacherType" from="${TeacherType?.values()}" keys="${TeacherType.values()*.name()}" required="" value="${teacherInstance?.teacherType?.name()}" disabled="false"/>
    </g:else>

Approach 2 works but I suppose if the number of conditional statements increase it may just be better to follow approach 1 and split the forms.

Is there another approach that I'm not aware of?

Answer 1

The disabled attribute of <g:select> (and many other <g:...> form field tags) can be a boolean-valued expression:

<g:select name="teacherType" from="${TeacherType?.values()}"
  keys="${TeacherType.values()*.name()}" required=""
  value="${teacherInstance?.teacherType?.name()}"
  disabled="${mode == 'edit'}"/>

This will render as disabled="disabled" if the expression evaluates to true, and as the absence of a disabled attribute (i.e. the field will not be disabled) if the expression is false. You could even use a boolean entry in the model, e.g. render the template with

model="[teacherInstance: teacherInstance, editing:true]"

(or editing:false respectively) and then say disabled="${editing}" on the <g:select>.