Type-checking Flux actions in TypeScript

FluxActions.ts

interface ActionClass<T extends Action> {
    prototype: T;
}

// Base class for actions
abstract class Action {
    type: string;
    constructor() {
        // Copy from the prototype onto the instance
        this.type = this.type;
    }
}

// Decorator to set type names for action classes
function typeName(name: string) {
    return function<T extends Action>(actionClass: ActionClass<T>) {
        actionClass.prototype.type = name;
    }
}

// Type guard for type checking
function isType<T extends Action>(action: Action, actionClass: ActionClass<T>): action is T {
    return action.type == actionClass.prototype.type;
}

// Actions have nominal types
type NominalType = void;

// Two sample actions:

@typeName("RemoveAppointment")
class RemoveAppointment extends Action {
    private _brand: NominalType;
    constructor(public appointmentId: number) {
        super();
    }
}

@typeName("RescheduleAppointment")
class RescheduleAppointment extends Action {
    private _brand: NominalType;
    constructor(public appointmentId: number, public date: Date) {
        super();
    }
}


// Example compile errors:

function doRemove(action: RemoveAppointment) {
    // ...
}

var action = new RescheduleAppointment(2553, new Date(2015, 10, 15));
doRemove(action); // Compile error!

function handleAction(action: Action) {
    if (isType(action, RemoveAppointment)) {
        action.date; // Compile error!
    }
}

I appreciate this approach very much! However, the redux document has a restriction on actions:

Actions are plain JavaScript objects

And the redux runtime do check actions before it dispatch. So an action with a constructor will raise an error.

Any idea to solve this?

@techird have a look at this thread comment: reduxjs/redux#992 (comment)