How to Implement Opportunity Gating in Apex

If you have your own custom "New" opportunity button that is a Visualforce page with Apex and you need to implement opportunity gating, you will need to write some Apex code to do so. Use the following code snippets as a guide for implementing opportunity gating in Apex. Note that while the code snippets shown here demonstrate the solution for a Visualforce controller, the logic is identical for Lightning components.

<!-- Visualforce Page -->

<apex:page standardController="Opportunity" extensions="MyOppController">
<!-- your VFPage page content here -->
</apex:page> 

// Apex controller

public with sharing class MyOppController
{
    public MyOppController(ApexPages.StandardController stdController)
    {
        // Required: If in Active Mode then opp must be created from a contact with an active response
        if(!FCRM.FCR_SupportAPI.IsPassiveMode())
        {
            // Optional: only use IsNonResponseByRecordType if you have record types implemented for your contacts. If no record types then remove only this one conditional statement.
            if(!FCRM.FCR_SupportAPI.IsNonResponseByRecordType(conid))
            {
                // Required: Opp must be created from a Contact
                String conid = ApexPages.currentPage().getParameters().get('conid');
                if(conid == null)
                {
                    // Add custom code here to prevent user from creating the opportunity. 
                    // You could display a message like "Opportunities must be created from a Contact"
                    // You could develop your page to show a JavaScript alert with a similar message
                }
 
                // Required: Contact must be part of an active campaign
                List<CampaignMember> activeResponses = FCRM.FCR_SupportAPI.GetActiveResponses(new List<Id>{conid});
                if(activeResponses.size() == 0)
                {
                    // Add custom code here to prevent user from creating the opportunity. 
                    // You could display a message like "To create an opportunity the contact must have an active repsonse"
                    // You could develop your page to show a JavaScript alert with a similar message
                    // You could redirect user back to the Contact after showing the message
                }
            }
 
            // Add code here to create opportunities based on the documentation at:
            // https://support.fullcircleinsights.com/Full_Circle_Response_Management/Response_Management_Admin_Zone/Response_Management_SDK/10_Extensibility_Functions/11_FCR_SupportAPI_Class
        }
    }
}