Action Function nulling out values unless rerender is specified?

Question

I have the following part in my visualforce page:

<apex:form>
    <apex:actionFunction name="interestInShowConfirmed" action="{!interestInShowConfirmed}" />
    <apex:actionFunction name="registerInterest" action="{!openInterestedInShowPopUp}" >
        <apex:param name="chosenId" value=""/>
    </apex:actionFunction>
</apex:form>

The way this code works, is that the "RegisterInterest" action function is called when a user clicks on a button (E.X. the button would execute: registerInterest('123213213'); ) - The register interest action function then generates a pop up to the user confirming their selection. Finally, when the user chooses the yes button on the pop up, the interestInShowConfirmed action function is called. I am running into a strange issue where I seemingly need to specify a re render target for these action functions or variable changes are not saved to the view state.

For example, this line of code

openPositionIdChosenForInterest = system.CurrentPageReference().getParameters().get('chosenId');

will return the correct passed Id if i specify a re render target for the "registerInterest" action function, but will return null if i do not. Also, if i specify a re render target only on "registerInterest" and not on "interestInShowConfirmed" - any global varriables set by the registerInterest action function will be null when "interestInShowConfirmed" tries to access them.

I'm guessing there is something I do not understand about re rendering and the view state - could someone fill me in?

Edit:

Here is how the registerInterest function is called. It is a button inside a custom component included in the visualforce page:

<apex:commandButton value="{!cell['buttonLabel']}" onClick="{!cell['javascriptToCallOnClick']}('{!cell['argToStoreOnClick']}');" reRender="None" />

Also, if i don't include a rerender in this button, my action function is not called

Answer 1

Not specifying reRender causes a POST request, while using reRender uses the AJAX library to perform the request. If you don't use a reRender, you must use the assignTo attribute of apex:param, as the parameters won't be posted (i.e. currentPage().getParameters() won't have any values).

The documentation is not particularly clear on this, but basically you need to either use assignTo or reRender; if you use neither, your parameters will be useless. This is true for other supported elements, like apex:actionSupport, when using parameters. You must use either attribute to have proper parameter support.