Typescript declaration: Merge a class and an interface

参考: https://stackoverflow.com/questions/47670959/typescript-declaration-merge-a-class-and-an-interface

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extend a enumeration with a method:

https://blog.oio.de/2014/03/21/declaration-merging-typescript/

enum UserType {
    ADMIN, USER, GUEST
}

module UserType {
    export function parse(value: string): UserType {
        var UT: any = UserType;
        if (typeof UserType[value] === "undefined") {
            throw new Error("unknown value of enum UserType: " + value);
        }
        return UserType[value];
    }
}
console.log(UserType.parse('0'));

　　

interface Box {
    height: number;
    width: number;
}
//----------------------------------------------
interface ClientModel extends Box{

}
// interface ClientModel extends Box { }
class ClientModel{
    public say():string{
        console.log(this.height);
        return '123421';

    }
}
let a = new ClientModel();
a.height = 123;
console.log(a.say());

　　

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ou can use declaration merging. If the class and the interface are declared in the same namespace/module and have the same name, they will be merged into a single class type.

interface ClientModel {
    name: string;
    email: string;
}

class ClientModel extends Model  {
    m() {
        this.email //Valid
    }
}

If you cannot change the interface or is declared in another namespace and you can't move it you can inherit from it in the merged interface:

interface Client {
    name: string;
    email: string;
}

interface ClientModel extends Client {}
class ClientModel extends Model  {
    m() {
        this.email //Valid
    }
}