Grails render template - ajax

Question

I have this <g:formRemote> having this attributes,
<g:formRemote name="innerForm" id="innerForm"
url="[controller:'user', action:'actionAJAX']"
update="formMessage">
<div id="formMessage">Fill up the fields</div>
<g:render template="form" bean="${newUser}" />
<div class="buttons">
<g:submitButton name="Create User"/>
<input type="reset" value="Cancel"/>
</div>
</g:formRemote>
which upon submit procceeds to a closure having this lines of codes,
def actionAJAX() {
def userInstance = new User(params)
render(template:"error", bean:userInstance)
}
_error.gsp would contain scaffold display of bean error in which violates the domain constraints (nullable, blank, etc.). It would look like this:
<g:hasErrors bean="${userInstance}">
<ul class="errors" role="alert">
<g:eachError bean="${userInstance}" var="error">
<li <g:if test="${error in org.springframework.validation.FieldError}">data-field-id="${error.field}"</g:if>><g:message error="${error}"/></li>
</g:eachError>
</ul>
</g:hasErrors>
message
The problem is that I can't display the errors of the bean [def userInstance = new User] on the _error.gsp. The scenario was only to leave all of the fields of _form.gsp (having the contents of the generate-view and removing all required attribute) but upon submit the closure only returns message on the <div id="formMessage"> which was expected to display all the errors of the domain that violates the domain constraints.

Answer 1

If that is all of the code you are showing, your main problem is you are not calling .validate() or .save(). You must call either one to get errors in your object.
def actionAJAX() {
User userInstance = new User(params)
if ( !user.save() )
{
render(template:"error", model:[userInstance: userInstance])
}
else
{
render(template:"success", model:[userInstance: userInstance])
}
}

Answer 2

Just a quick look at the code, so maybe I'm missing one of many Grails conventions, but you are passing to the render method the userInstance with 'bean' as map key. And then referring to it as ${userInstance}. Try to refer it as ${bean} inside the templeta or pass it like:
render(template:"error", userInstance:userInstance)
It's not an answer for your question, just an additional tip: you can use g:renderErrors tag inside your error template or even instead of it.