formbinding

grails unchecked checkbox String and List<String> don't bind correctly

An empty passed "_${field}" which tells the binding to set an empty or false value, but this only works for boolean values. If the value is a String or a List, empty behavior is not correctly performed.

A very simple example where we want to map checkboxes to String values:

class Person {

	String name
	List<String> languages
	String comments
	boolean engineer

    static constraints = {
    	name()
    	languages nullable: true
    	comments nullable: true
    	engineer nullable: true
    }
}

Using the following form:

          <g:form resource="${this.person}" method="PUT">
               <g:hiddenField name="version" value="${this.person?.version}" />
               <fieldset class="form">
                   <div class='fieldcontain required'>
                       <label for='name'>Name</label>
                       <g:textField name="name" value="${person.name}" />
                   </div>
                   <div class='fieldcontain'>
                       <label for='languages'>Languages</label>
                       English<g:checkBox name="languages" value="English" checked="${this.person.languages?.contains('English')}" /> &nbsp; 
                       Spanish<g:checkBox name="languages" value="Spanish" checked="${this.person.languages?.contains('Spanish')}" /> &nbsp;
                       French<g:checkBox name="languages" value="French" checked="${this.person.languages?.contains('French')}" />
                   </div>
                   <div class='fieldcontain'>
                       <label for='comments'>Comments</label>
                       Likes Cats<g:checkBox name="comments" value="Likes Cats" checked="${this.person.comments == 'Likes Cats'}" />
                   </div>
                   <div class='fieldcontain'>
                       <label for='engineer'>Engineer</label>
                       <g:checkBox name="engineer" value="true" checked="${this.person.engineer}" />
                   </div>
               </fieldset>
               <fieldset class="buttons">
                   <input class="save" type="submit" value="${message(code: 'default.button.update.label', default: 'Update')}" />
               </fieldset>
           </g:form>

The checkbox behavior binds correctly for boolean, String, and List values, BUT when a String value is unchecked, it does not bind the null state, and when a List values are unchecked, it works as expected until you uncheck the last value. It does not correctly bind the empty state.

A Simple example

grails create-app formbinding
grails
create-domain-class Person
generate-all Person
# modify Person.groovy, create.gsp and edit.gsp
run-app