Data-driven decimal places

Attributes passed to custom components from Visualforce pages can be used wherever the merge syntax is legal. The <apex:outputText /> standard component can be used to format numeric and date values, but the formatting is limited to literal values rather than merge fields. In this scenario, an attribute indicating the number of decimal places to display for a numeric value cannot be used directly in the <apex:outputText /> component.

In this recipe we will create a custom component that accepts attributes for a numeric value and the number of decimal places to display for the value. The decimal places attribute determines which optional component is rendered to ensure that the correct number of decimal places is displayed, and the component will also bracket negative values. A Visualforce page will also be created to demonstrate how the component can be used.

How it works…

Opening the following URL in your browser displays the DecimalPlacesDemo page: https://<instance>/apex/DecimalPlacesDemo.

Here, <instance> is the Salesforce instance specific to your organization, for example, na6.salesforce.com.

The Visualforce page iterates a number of opportunity records and delegates to the component to output the opportunity amount, deriving the number of decimal places from the amount.

<c:DecimalPlaces dp="{!TEXT(MOD(opp.Amount/10000, 5))}"
  value="{!opp.Amount}" />

The component conditionally renders the appropriate output panel, which contains two conditionally rendered <apex:outputText /> components, one to display a positive value to the correct number of decimal places and another to display a bracketed negative value.

<apex:outputPanel rendered="{!dp=='1'}">  
  <apex:outputText rendered="{!AND(NOT(ISNULL(VALUE)), value>=0)}"
                value="{0, number, #,##0.0}">
    <apex:param value="{!value}"/>
  </apex:outputText>
  <apex:outputText rendered="{!AND(NOT(ISNULL(VALUE)), value<0)}"
                value="({0, number, #,##0.0})">
    <apex:param value="{!ABS(value)}"/>
  </apex:outputText>
</apex:outputPanel>