Learn TypeScript 3 by Building Web Applications

Adding class-transformer decorators to domain classes

First of all, since we are going to use decorators, we need to adapt the tsconfig.json file to add support for them (actually, to remove warnings):

1. Edit the file and set the experimentalDecorators option to true.

Next, import the decorators from class-transformer.

2. Add the following import statement at the top of the mediaman.ts file: import {classToPlain, plainToClassFromExist, Expose, Type} from "class-transformer";.

Finally, you also need to import reflect-metadata.

3. Add the import statement, import "reflect-metadata";, at the top of the file (that is, before the class-transformer imports).
4. Now, adapt the MediaCollection class as follows:

class MediaCollection<T extends Media> ...