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Priyanka ITSPriyanka ITS 

How to implement an interface?

Best Answer chosen by Priyanka ITS
Khan AnasKhan Anas (Salesforce Developers) 
Hi Priyanka,

Greetings to you!

To use an interface, another class must implement it by providing a body for all of the methods contained in the interface.

Defining an interface is similar to defining a new class. For example, a company might have two types of purchase orders, ones that come from customers, and others that come from their employees. Both are a type of purchase order. Suppose you needed a method to provide a discount. The amount of the discount can depend on the type of purchase order.

You can model the general concept of a purchase order as an interface and have specific implementations for customers and employees. In the following example the focus is only on the discount aspect of a purchase order.
Here is the definition of the PurchaseOrder interface. 
// An interface that defines what a purchase order looks like in general
public interface PurchaseOrder {
    // All other functionality excluded
    Double discount();
}

This class implements the PurchaseOrder interface for customer purchase orders. 
// One implementation of the interface for customers
public class CustomerPurchaseOrder implements PurchaseOrder {
    public Double discount() {
        return .05;  // Flat 5% discount
    }
}

This class implements the PurchaseOrder interface for employee purchase orders. 
// Another implementation of the interface for employees
public class EmployeePurchaseOrder implements PurchaseOrder {
      public Double discount() {
        return .10;  // It’s worth it being an employee! 10% discount
      } 
}

Note the following about the above example:
  • The interface PurchaseOrder is defined as a general prototype. Methods defined within an interface have no access modifiers and contain just their signature.
  • The CustomerPurchaseOrder class implements this interface; therefore, it must provide a definition for the discount method. Any class that implements an interface must define all the methods contained in the interface.

Please refer to the below links which might help you further.

https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_classes_interfaces.htm

https://www.tutorialspoint.com/apex/apex_interfaces.htm

https://www.tutorialkart.com/learn_apex/what-is-an-interface-in-apex/

http://bobbuzzard.blogspot.com/2017/10/programming-against-apex-interfaces.html

I hope it helps you.

Kindly let me know if it helps you and close your query by marking it as solved so that it can help others in the future. It will help to keep this community clean.

Thanks and Regards,
Khan Anas

All Answers

Khan AnasKhan Anas (Salesforce Developers) 
Hi Priyanka,

Greetings to you!

To use an interface, another class must implement it by providing a body for all of the methods contained in the interface.

Defining an interface is similar to defining a new class. For example, a company might have two types of purchase orders, ones that come from customers, and others that come from their employees. Both are a type of purchase order. Suppose you needed a method to provide a discount. The amount of the discount can depend on the type of purchase order.

You can model the general concept of a purchase order as an interface and have specific implementations for customers and employees. In the following example the focus is only on the discount aspect of a purchase order.
Here is the definition of the PurchaseOrder interface. 
// An interface that defines what a purchase order looks like in general
public interface PurchaseOrder {
    // All other functionality excluded
    Double discount();
}

This class implements the PurchaseOrder interface for customer purchase orders. 
// One implementation of the interface for customers
public class CustomerPurchaseOrder implements PurchaseOrder {
    public Double discount() {
        return .05;  // Flat 5% discount
    }
}

This class implements the PurchaseOrder interface for employee purchase orders. 
// Another implementation of the interface for employees
public class EmployeePurchaseOrder implements PurchaseOrder {
      public Double discount() {
        return .10;  // It’s worth it being an employee! 10% discount
      } 
}

Note the following about the above example:
  • The interface PurchaseOrder is defined as a general prototype. Methods defined within an interface have no access modifiers and contain just their signature.
  • The CustomerPurchaseOrder class implements this interface; therefore, it must provide a definition for the discount method. Any class that implements an interface must define all the methods contained in the interface.

Please refer to the below links which might help you further.

https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_classes_interfaces.htm

https://www.tutorialspoint.com/apex/apex_interfaces.htm

https://www.tutorialkart.com/learn_apex/what-is-an-interface-in-apex/

http://bobbuzzard.blogspot.com/2017/10/programming-against-apex-interfaces.html

I hope it helps you.

Kindly let me know if it helps you and close your query by marking it as solved so that it can help others in the future. It will help to keep this community clean.

Thanks and Regards,
Khan Anas
This was selected as the best answer
Priyanka ITSPriyanka ITS
Thanks for the response