how to get several same object values in a Grails form - forms

Question

let's take a simpe domain class:
class Person { String aname }
A gsp form to let the user input a person is easy:
<g:form ...>
...
someone:<input name="aname">
...
</g:form>
... and back in the controller, to get the values, I can just write
def p = new Person(params)
Now, I'd like to let the user input the data for two persons (let's say, two parents) in the same form. How to write this ? I just can't give the same name for the two input fields, but if I don't keep the original property name ("aname"), back in the controller I will have to handle by hand the bindings between the name of the property, and the form input names:
<g:form ...>
...
father:<input name="aname1">
mother:<input name="aname2">
...
</g:form>
then, in controller
def p1 = new Person(); p1.aname = params.aname1
def p2 = new Person(); p2.aname = params.aname2
Is there a way to keep the automatic binding facility even if there is several objects of same types given in a form ?

Answer 1

Try to use this way:
<g:form ...>
...
father:<input name="father.aname">
mother:<input name="mother.aname">
...
</g:form>
And controller:
def p1 = new Person(params.father);
def p2 = new Person(params.mother);

Answer 2

I suppose you are thinking of doing something like this:
<g:form ...>
...
father:<input name="aname">
mother:<input name="aname">
...
</g:form>
which would result as ?aname=Dad&aname=Mom
You can handle them in controller as below:
params.list('aname').each{eachName -> //Persist each `aname`}
Have a look at Handling Multi Parameters.

Answer 3

the dot notation in the "name" attribute works well for the <input> tag.
To go further, there is also a solution for the "fields" plugin: rather than using the "name" attribute, one should use the "prefix" one, as described here.
For example:
<f:field bean="mother" property="forename" prefix="mother."/>
<f:field bean="mother" property="surname" prefix="mother."/>
<f:field bean="father" property="forename" prefix="father."/>
<f:field bean="father" property="surname" prefix="father."/>
we can even write it better, with help of <f:with> tag:
<f:with bean="mother" prefix="mother.">
<f:field property="forename"/>
<f:field property="surname"/>
</f:with>
<f:with bean="father" prefix="father.">
<f:field property="forename"/>
<f:field property="surname"/>
</f:with>