How to define correct Map<X,Y> type in typescript where Y will be any child class of Parent?

Question

I have some Parent class and amount of Child classes that extends parent. I need to define Map<sting,Y> where Y can be any of Child classes. If I try to define it as Map<string, Parent> I got transpilation error

error TS2345: Argument of type 'typeof Child' is not assignable to parameter of type 'Parent'. Property 'someParentMethod' is missing in type 'typeof Child'.

As Child automatically inherits someParentMethod from Parent I don't re declare in Child class. What is the correct way of declare needed Map argument type, so that it accepted any Child class instances?

Is the Map supposed to hold instances of Child or constructors of Child? Please post the code that gives the error. It looks like you are passing in a constructor where it expects an instance. — jcalz
@jcalz Thanks. The problem is exactly that I'm passing constructor, instead of instance. I actually need to pass the constructors. Would you be so kind, to tell ss there a way to define type so that it accepted constuctor of any Child. Example simplified code that raises mentioned error is below. Thanks in advance. ` class a { public x; } class b extends a { } let m:Map<string, a> = new Map([['a',b]]); ` — user3687562

Rodris Rodris · Accepted Answer · 2017-09-18T17:33:17

Looks like you are only missing a typeof.

class a { public x; someParentMethod: () => void }
class b extends a { }

let m: Map<string, typeof a> = new Map([['a', b]]);

How to define correct Map<X,Y> type in typescript where Y will be any child class of Parent?

1 Answers