Package developers can use conditional logic in Apex classes and triggers to exhibit different behavior for different versions. This allows the package developer to continue to support existing behavior in classes and triggers in previous package versions while continuing to evolve the code.
When subscribers install multiple versions of your package and write code that references Apex classes or triggers in your package, they must select the version they are referencing. Within the Apex code that is being referenced in your package, you can conditionally execute different code paths based on the version setting of the calling Apex code that is making the reference. The package version setting of the calling code can be determined within the package code by calling the System.requestVersion method. In this way, package developers can determine the request context and specify different behavior for different versions of the package.
The following sample uses the System.requestVersion method and instantiates the System.Version class to define different behaviors in an Apex trigger for different package versions.
trigger oppValidation on Opportunity (before insert, before update) { for (Opportunity o : Trigger.new){ // Add a new validation to the package // Applies to versions of the managed package greater than 1.0 if (System.requestVersion().compareTo(new Version(1,0)) > 0) { if (o.Probability >= 50 && o.Description == null) { o.addError('All deals over 50% require a description'); } } // Validation applies to all versions of the managed package. if (o.IsWon == true && o.LeadSource == null) { o.addError('A lead source must be provided for all Closed Won deals'); } } }
For a full list of methods that work with package versions, see Version Class and the System.requestVersion method in System Class.
The request context is persisted if a class in the installed package invokes a method in another class in the package. For example, a subscriber has installed a GeoReports package that contains CountryUtil and ContinentUtil Apex classes. The subscriber creates a new GeoReportsEx class and uses the version settings to bind it to version 2.3 of the GeoReports package. If GeoReportsEx invokes a method in ContinentUtil which internally invokes a method in CountryUtil, the request context is propagated from ContinentUtil to CountryUtil and the System.requestVersion method in CountryUtil returns version 2.3 of the GeoReports package.