apex:repeat tag won't increment apex:variable

Question

Below is a snippet of code in which an apex:variable is not increment inside an apex:repeat tag. In this case, the var="rowCount" gets incremented without any issues, but the var="headerCount" does not increment at all. Can anyone provide some insight?

Sample Code

<apex:pageBlock >
      <!-- Tracks the row in the table -->
      <apex:variable var="rowCount" value="{!-1}" />// This variable increments properly
      <apex:variable var="headerCount" value="{!0}" />// This variable does not increment at all

      <apex:pageBlockSection columns="1" title="{!Title}" id="pbSec">
          <apex:pageBlockTable value="{!sObjRecords}" var="sObj" styleClass="dataTable table table-fixedheader" id="pageBlockTable">
              <!-- Displays the multiple columns based on the user input -->

              <apex:repeat value="{!Fields}" var="fld">
                  <apex:column >

                    <apex:outputText value="{!sObj[fld]}"/>

                    <apex:facet name="header">{!headers[headerCount]}</apex:facet>
                      <apex:variable var="headerCount" value="{!headerCount+1}" />
                  </apex:column>
              </apex:repeat>

              <!-- Action Column with buttons - May not be used if attribute is false -->
              <apex:column rendered="{!IsActionColumnEnabled}" >
                  <apex:facet name="header">{!$Label.YAHS_PRT_Action}</apex:facet>
                  <apex:repeat value="{!Buttons}" var="button">

                  <apex:variable var="rowCount" value="{!rowCount+1}" />

Answer 1

please refer to Salesforce documentation for apex:variable.

Note: apex:variable does not support reassignment inside of an iteration component, such as apex:dataTable or apex:repeat. The result of doing so, e.g., incrementing the as a counter, is unsupported and undefined.

Regardless of few confusions in your code, this design (using variable inside repeat) will never work perfectly and will always leave a possibility for random failures.

I suggest you to use apex:repeat as it was originally intended - as a repeat over a collection of elements. There is always other way to iterate over something then incrementing a apex:variable.

Answer 2

The safe way to retrieve a value from a collection of values inside <apex:repeat> is to use a Map, e.g. Map<String, String> in your case, where the key is the field name and the value is the header for the field. Maps use the same syntax in VisualForce as Lists, so your code looks something like:

<apex:repeat value="{!myList}" var="myVar">
    <apex:outputText value="myMap[myVar]" />
</apex:repeat>

Unfortunately, I don't know of any obvious way to duplicate this functionality without a custom controller or extension. If the value you are iterating over happens to be a primitive or you only need an iterating number, you can use Javascript to get similar functionality:

<script>
    var myVarList = new Array();
    var iteratorForList = 0;
    <apex:repeat value="{!myVarList}" var="myVar">
        myVarList.push('{!myVar}');
    </apex:repeat>
</script>
<apex:repeat value="{!otherControllerList}" var="myOtherVar">
    <apex:outputText id="textPlacer" />
    <script>
        document.querySelector('#{!$Component.textPlacer}').innerText = myVarList[iteratorForList];
        iteratorForList++;
    </script>
</apex:repeat>

Answer 3

You could simply re-declare the variable at the end of your repeat iteration and increment it within the repeat like this...

    <apex:variable var="iter" value="1" />
    <apex:repeat value="{!myList}" var="lis">
        .... all your page elements here

        <apex:variable value="{!iter+ 1}" var="iter" />
    </apex:repeat>

this has worked for me in the past.