At what point is it appropriate for a class to incorporate an interface?

Currently working on a project and I've noticed developers using TypeScript in the following way:


        export class Ledger implements ILedger {
            LedgerID: number;
            CashAmmount: number;
            Units: number;

            public static someFunction {
                // an ajax call, for example, to a controller
            }
        }

        export interface ILedger {
            LedgerID: number;
            CashAmmount: number;
            Units: number;
        }
    

I'm questioning whether this is the correct approach. It seems redundant to have no implementation in the class. Additionally, in our React components, there are references to either the interface or the class. I'd like to establish some guidelines but first need guidance on what the best practice is in this scenario.

Answer №1

It seems rather pointless if there is no actual implementation in the class.

I completely agree. In those situations, there really is no need for it. However, there are definitely valid use cases where it can be quite beneficial.

Implementing Dependency Injection

Consider utilizing a library like: https://github.com/inversify/InversifyJS

Adhering to external APIs

For instance, if someone requests an interface like IFoo, you may want to incorporate a class from your codebase that adheres to this interface. By extending the class accordingly, you can ensure that it always aligns with the external IFoo.

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