What is Interface in Salesforce?

By
Amit Singh
-
0
576

Conclusion

By providing a clear separation between a method declaration and implementation, interfaces enable the addition of an abstraction layer to code. As a result, it becomes possible to have different implementations of a method based on specific conditions.

Table of Contents

  1. Conclusion
  2. Recap to previous Session
  3. Introduction to Interface
  4. Interface Declaration
  5. Examples
  6. Interface
  7. Hands-On Code
  8. Watch Complete Video
  9. Resources

Recap to previous Session

In the previous session, we learned how inheritance works in Salesforce.

Introduction to Interface

By providing a clear separation between a method declaration and implementation, interfaces enable the addition of an abstraction layer to code. As a result, it becomes possible to have different implementations of a method based on specific conditions.

  • Within a class that is the interface, we can only define methods.
  • The interface cannot provide the implementations for its method.
  • The visibility of the methods will be controlled by the class that is implementing the interface.
  • In the interface, we cannot define any properties or variables except the methods.
  • Multiple interfaces can be implemented by a Single class.
  • A single interface can be implemented by Multiple Classes.
  • An Interface can extend another interface.
  • An interface can not be instantiated means an object can not be created

Interface Declaration

// Interface Declaration
<Access Modifier> interface <Class Name>
public interface Vehicle{
   public String methodName();
}

// Interface Declaration
<Access Modifier> interface <Class Name>
public interface Bank{
   public String methodName();
}

Examples

As an example, we can take from the Banks where every bank has its own interest for a different type of loans. Here is how the Apex Class will look like that is implementing the interface

Hands-On –

  • Implement discounts using the IPurchaseOrder Interface.
  • Implement Payment processing with IPaymentProcessor

Interface

public interface IBank{
    public Decimal homeLoanInterest();
    public Decimal carLoanInterest();
    public Decimal personalLoanInterest();
    public Decimal educationLoanInterest();
}

The class that implements the interface. To implement the interface, we need to use implements keywords

public class SBIBank implements IBank{
    public Decimal homeLoanInterest(){

    }
    public Decimal carLoanInterest(){

    }
    public Decimal personalLoanInterest(){

    }
    public Decimal educationLoanInterest(){

    }
}
public class ICICIBank implements IBank{
    public Decimal homeLoanInterest(){

    }
    public Decimal carLoanInterest(){

    }
    public Decimal personalLoanInterest(){

    }
    public Decimal educationLoanInterest(){

    }
}
public class PNBBank implements IBank{
    public Decimal homeLoanInterest(){

    }
    public Decimal carLoanInterest(){

    }
    public Decimal personalLoanInterest(){

    }
    public Decimal educationLoanInterest(){

    }
}

Hands-On Code

public interface IVehicle {
    void start();
    void stop();
    String changeGear(); // method delcare
    Boolean openDoor(String doorType);
}
public interface IDML {
}
public class Mercedes implements IVehicle, IDML, Database.Stateful, Database.AllowsCallouts {
    // method implementations
    public void start(){
        System.debug('Start');
    }
    // method implementations
    public void stop(){
        System.debug('stop');
    }
    // method implementations
    public String changeGear(){
        System.debug('change gear');
        return '';
    }
    // method implementations
    public Boolean openDoor(String doorType){
        return true;
    }
}
public class Jaguar implements IVehicle {
    // method implementations
    public void start(){
        System.debug('Start');
    }
    // method implementations
    public void stop(){
        System.debug('stop');
    }
    // method implementations
    public String changeGear(){
        System.debug('change gear');
        return '';
    }
    // method implementations
    public Boolean openDoor(String doorType){
        return true;
    }
}
public interface IPurchaseOrder {
    Decimal discount();
}
public class NewCustomerDiscount implements IPurchaseOrder {
    public Decimal discount(){
        return 1.6;
    }
}
public class CustomerDiscount implements IPurchaseOrder {
    public Contact customer;
    public Decimal discount(){
        DateTime oneYearOld = System.now().addYears(-1);
        DateTime twoYearOld = System.now().addYears(-2);
        if( this.customer.CreatedDate > oneYearOld ){
            return 2.3;
        }else if( this.customer.CreatedDate > twoYearOld ){
            return 4.5;
        }
        return 1.6;
    }
}
public interface IPaymentProcessor {
    void processPayment(Decimal amount);
    void processRefund(Decimal amount, Boolean isFullRefund);
}
public class CreditCardPayment implements IPaymentProcessor {
    public void processPayment(Decimal amount){

    }
    public void processRefund(Decimal amount, Boolean isFullRefund){

    }
}
public class VISADebitCardPayment implements IPaymentProcessor {
    // VISA
    // AMEX
    // MasterCard
    public void processPayment(Decimal amount){
        System.debug(' VISADebitCardPayment => '+ amount);
    }
    public void processRefund(Decimal amount, Boolean isFullRefund){

    }
}
public class VISADebitCardProcessor {

    // IPaymentProcessor processor - Generic
    public void processPayment(Decimal amount, IPaymentProcessor processor){
        // Run Time pe decide karega
        processor.processPayment(amount);
    }

}
VISADebitCardPayment card = new VISADebitCardPayment();
VISADebitCardProcessor payment = new VISADebitCardProcessor();
payment.processPayment(234, card );

Watch Complete Video

Resources

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