How to pass an object to a java method using a4j:commandbutton - jsf

Question

I have a rich:modal panel (code below). I want to pass the #{currentLeg} to the method called in action="#{legHandler.assignAndInitLoadPlanning}. But when I debug, at the method legHandler.assignAndInitLoadPlanning, resolveVariable("currentLeg"); returns an object with all its attribute values equal to null. It's attributes should not be null.
Additionally, this rich:modal is called from an a4j:commandLink onclick="showUnitDialog(); on the same jsp file. If I change this said onclick to onclick="#{legHandler.assignAndInitLoadPlanning}" the currentleg will be passed properly but i cannot do this because i need to have a popup (which is a rich:modalpanel) to display. And I am using JSF 1.
I've already tried keep alive and set variable but still not works. It seems that the currentLeg is not properly passed. Do you have any idea why?
<rich:modalPanel id="unitDialog" width="400" height="100">
<f:facet name="header">
<h:panelGroup>
<h:outputText value="Please Select Unit for the Leg"></h:outputText>
<h:outputText value="#{currentLeg.legId}"></h:outputText>
</h:panelGroup>
</f:facet>
<h:panelGrid width="100%" columns="2" columnClasses="colStyle1, colStyle2">
<h:selectOneRadio value="legHandler.unit">
<f:selectItem itemValue="kg" itemLabel="kg" />
<f:selectItem itemValue="lb" itemLabel="lb" />
</h:selectOneRadio>
</h:panelGrid>
<h:panelGrid style="text-align: center" columns="3"
columnClasses="col1, col2" width="100%">
<a4j:commandButton value="Apply" styleClass="big_btn"
id="applyButton" immediate="true"
action="#{legHandler.assignAndInitLoadPlanning}"
oncomplete="{#{rich:component('unitDialog')}.hide();}">
</a4j:commandButton>
<a4j:commandButton value="Cancel" styleClass="big_btn"
immediate="true"
id="closeUnitPopupDialog"
onclick="#{rich:component('unitDialog')}.hide();"/>
</h:panelGrid>
</rich:modalPanel>

Answer 1

If you're using EL 2.2+ you can simply pass the value as parameter:
<a4j:commandButton action="#{legHandler.assignAndInitLoadPlanning(currentLeg)}" … />
Otherwise use a4j:actionparam and save the value to the bean
<a4j:commandButton …>
<a4j:actionparam name="currentLeg" value="#{currentLeg}" assignTo="#{legHandler.currentLeg}" />
<a4j:commandButton>