Typescript - Array of extended Classes of specific Parent

Question

I have an abstract class called Action:

abstract class Action { ... }

And I have several classes that extend Action:

class Vote extends Action { ... }
class Upload extends Action { ... }
...

How can I declare an array of classes that extends Action (but shouldn't accept Action itself?

const actions: (typeof Action)[] = [
  Vote,    // OK (passes)
  Upload,  // OK (passes)
  File,    // OK (fails)
  Action   // BAD (passes)
]

Titian Cernicova-Dragomir · Accepted Answer · 2019-08-16 08:43:43Z

5

Use a constructor signature that returns the abstract class instead of the abstract class. The abstract class does not have a constructor in the type system so it won't be valid but any derived class inheriting the abstract class will be valid.

abstract class Action { ... }

class Vote extends Action { ... }
class Upload extends Action { ... }

const actions: (new () => Action)[] = [
  Vote,    // OK (passes)
  Upload,  // OK (passes)
  File,    // OK (fails)
  Action   // Ok now (fails)
]

answered Aug 16, 2019 at 8:43

Titian Cernicova-Dragomir

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