Aura:if use a function as expression

Question

I wish to check a condition inside an aura:iteration. The condition should be dynamically set according to the current item in the iteration.

I'm trying to achieve the following :

<aura:if isTrue="{!c.myTestFunction(parameter)}">
    <!-- ... -->
</aura:if>

With the following in controller :

myTestFunction : function(parameter) { ... }

Of course this is not working. So my question is : is there any workaround to achieve this ? I would like not to update my iteration objects with a new property "toDisplay" that would require many updates.

Answer 1

It could be very useful sometimes, but you can't call methods like that (you can only invoke them with events) and you can't pass parameters to them. So in your case, I would recommend creating a component that you render in your iteration:

<aura:iteration items="{!v.myObjects}" var="obj">
    <c:yourComponent value="{!obj}" param="{!v.parameter}" />
</aura:iteration>

And your component could look like this:

<aura:component>
    <aura:attribute name="value" type="Object">
    <aura:attribute name="param" type="String">
    <aura:attribute name="isRendered" type="Boolean" access="private">

    <aura:handler name="init" value="{!this}" action="{!c.doInit}"/>

    <aura:if isTrue="{!v.isRendered}">
        <!-- ... -->
    </aura:if>
</component>


doInit: function(cmp) {
    var rendered = //doSomethingWithParam
    cmp.set("v.isRendered", rendered);
}

Answer 2

You have only two choices here:

<aura:if isTrue="{!currentItem.display}">

Or

<aura:if isTrue="{!eq(currentItem.display, 'some value')}">

If you really need a function, you do need an attribute you can bind to, so you'll want to initialize the value as part of the attribute. You can't call a method with parameters, and you can't call a method period except in situations where it's allowed (primarily the action parameter of most components that have it, as well as event handlers like onclick or pressed), and even those don't accept parameters.