inheritance in typescript interface

In this TypeScript tutorial we learn about interfaces that have no member implementation, forcing developers to follow a specific design and allowing us to build loosely coupled applications. In an interface, variables and methods are only declared. typescript If we decided to add a Bunny class, all we need to do is implement the IHoppable interface. We implement an interface with the implements We cover defining and implementing one or more interfaces, as well as how to implement the members of an interface. Please note that interfaces arent used for multiple inheritance, its just a benefit we get when using an interface. And the objects declared as specific Interface type should define values for variables and implement methods declared in the interface. Interface is an object oriented concept which helps objects of an Interface type contains same properties and methods.

interface body contains variables and methods declarations. Interfaces arent inherited, but rather implemented. To implement multiple interfaces, we separate them with a comma. For example, consider Car as an interface that has properties: number of wheels, side mirrors, and method : breaking(), acceleration(), turn(), etc. If a class does not implement their own version of the methods in the interface, the compiler will raise an error. In TypeScript, Interface is a deal that the objects of the type should contain properties and functions declared in the interface. Objects of an interface type cannot declare any new methods or variables. Interfaces force a developer to provide their own implementation. keyword. An interface is like a class whose members arent implemented. Inheritance makes our classes tightly coupled and dependent on each other. If a method exists in the interface, a developer has to implement a version of it. A popular convention is to prefix the interface name with the capital letter I, to know at a glance that its an interface. In this TypeScript Tutorial, we have learnt how to create an interface and how objects of an interface type are created that implement the interface with examples. Nothing breaks or needs to be changed because its all loosely coupled. Inheritance can be abused, which may lead to a large, fragile hierarchy of classes. Because a sparrow can both fly and hop around, it can implement both interfaces.

In the example above, we create another interface called IHoppable. Both Sparrow and Plane classes implement the IFlyable interface and both have to implement their own versions of the fly() method. Interfaces are define the same way as classes, except we use the interface Instead of defining a class for each relationship, we define interfaces. Even though an interface has nothing to do with inheritance, it does allow for polymorphic behavior in a similar way. Interface members arent implemented. Its similar to what we did in the lesson on composition but with interfaces, we force other developers to follow our design. We use cookies to ensure you get the best experience on our website. A super class declares and defines variables and methods. We want them to be as loosely coupled as possible. Interface enforces the variables and methods that has to be present in an object. - Copyright - TutorialKart 2021, Salesforce Visualforce Interview Questions. A car company can create a car with its own interests, butany car that is created (car object of type Car interface), should implement methods and define variables that are present in the interface. To recap quickly: Interfaces allow us to have easy has-a relationships between classes. JavaScript file when the above .ts while is compiled using tsc : This example only demonstrates how to declare an interface and how objects of the interface type are created. A sub class extends the capability of a super class to suit the custom needs. A sub class that inherits a super class, can declare and define its own variables and methods. Another benefit of interfaces is that we can implement more than one. In the example above, we dont have the fly() method in our Sparrow class, so the compiler raises an error. One may appreciate interface concept when the architect or developer does not know the implementation, but definitely knows about the parameters and the methods that has to be there.

keyword instead of the class keyword. Thus an Interface contains only the declarations of variables(properties) and methods(behaviors). Classes can implement multiple interfaces. The actual implementation may change from object to object. We dont initialize properties with values, or add code blocks to methods, although they can contain parameters. Following are the main differences between interface and inheritance : Following is the syntax to declare and define an interface : Following is a simple Interface called Student, which has two variables declared: name and rollNumber, and one method : displayInformation(). If you remember from our tutorial on composition, we spoke about favouring a has-a relationship over an is-a relationship.