How to write post installer script apex class for package?

Question

i have a custom setting named lendingxl__LeadApplicationFieldMapping__c in my org. i want to create it's record after installing the package. & update the same records after upgrading the package. So How should i write the apex class for it ?

Answer 1

This is the pattern we use:

global class YourInstallHandler implements InstallHandler {

    private Version previousVersion;

    global void onInstall(InstallContext context) {
        if (context.previousVersion() != null) {
            previousVersion = context.previousVersion();
            doUpgrade();
        } else {
            doInstall();
        }
    }

    private void doUpgrade() {
        // Version upgrade steps with more added over time
        if (isInstalledVersionBefore(new Version(1, 3))) {
            ...
        }
        if (isInstalledVersionBefore(new Version(1, 12))) {
            ...
        }
        if (isInstalledVersionBefore(new Version(2, 3))) {
            ...
        }
        ...
    }


    private void doInstall() {
        // Any first time install logic
        ...
    }

    private Boolean isInstalledVersionBefore(Version version) {
        return previousVersion.compareTo(version) < 0;
    }
}

where over time more version upgrade steps are added.

Answer 2

Well you have to implement the InstallHandler interface so that after installation the methods defined would work.

https://developer.salesforce.com/docs/atlas.en-us.packagingGuide.meta/packagingGuide/apex_post_install_script_create.htm

There are context variables like context.isUpgrade() / context.isPush() that will tell you if its a first installation or push instalation.

Similarly you can delete the data via implementing UninstallInterface. https://developer.salesforce.com/docs/atlas.en-us.packagingGuide.meta/packagingGuide/apex_uninstall_script_intro.htm

As you said you have to update your custom settings value, I would suggest you to not use any InstallScript and replace custom setings via custom metadata types. Records of custom metadata types can be deployed.