Specifying type with class and interface in TypeScript

Question

My background comes from Objective-C where you can specify types that have both classes and interfaces in them. I can't seem to find any documentation that shows this in TypeScript, but it must exist, right?

Here's an example:

class Vehicle {}
class Car extends Vehicle {}
class Truck extends Vehicle {}

interface Electric{}

// These next lines are WRONG!
ChargeMyCar(car: Car<Electric>) { ... }
ChargeMyTruck(truck: Truck<Electric>) { ... }

Is this possible? What's the syntax?

How about a type that has multiple interfaces?

Brent - after reading your question a few times, I'm not sure what you're looking for. Perhaps you could show what code you're using in Objective-C and then it might be clearer what the similar TypeScript would be. — NYCdotNet
– NYCdotNet, Commented Dec 22, 2014 at 20:43

wjohnsto · Accepted Answer · 2014-12-22 21:13:55Z

2

It really depends on what you are trying to do with the Electric interface. You can use the following syntax:

class Vehicle {
    fuel: any;
}
class Car<T> extends Vehicle {
    fuel: T;
}
class Truck<T> extends Vehicle {
    fuel: T;
}

interface Electric {}

ChargeMyCar<T extends Electric>(car: Car<T>) { ... }
ChargeMyTruck<T extends Electric>(truck: Truck<T>) { ... }

The above example shows that a car/truck takes an abstract type of fuel, and in order to "charge" a car/truck, you must have a car/truck with Electric type fuel. Kind of a silly example, but do you understand the syntax?

Multiple interfaces is easy, if you wanted to use multiple interfaces instead you could just do the following:

class Vehicle {
    fuel: any;
}
class Car extends Vehicle { }
class Truck extends Vehicle { }

interface Electric { }

class ElectricCar implements Vehicle, Electric { }
class ElectricTruck implements Vehicle, Electric { }

ChargeMyCar(car: ElectricCar) { ... }
ChargeMyTruck(truck: ElectricTruck) { ... }

edited Dec 22, 2014 at 21:13

answered Dec 22, 2014 at 20:44

wjohnsto

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2 Comments

Brent Traut Over a year ago

After looking around a bunch more, I think this is the right answer. I didn't expect to have to make an ElectricCar and ElectricTruck type, but it seems like it's the easiest answer.

wjohnsto Over a year ago

another implementation could be class ElectricCar extends Car implements Electric { }, this may be what you're looking for.

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