lilac rampart
I am trying to set the return type on a function.
export const getModels = <T extends new () => Model>(): T[] => [UserDetail];
The return is an array of classes extending from the Model class from sequelize-typescript. But I am getting the error:
Type 'typeof UserDetail' is not assignable to type 'T'. 'typeof UserDetail' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint 'new () => Model<any, any>'
next marlin
T isn't used in the parameter list, this is basically the generic as typecast pattern
the generic should probably be on the returned function misread
although, you might not even need/want the generic if you want to allow multiple different classes
generics in methods aren't very useful if they're only used once
lilac rampart
generics in methods aren't very useful if they're only used once
I have eslint rule for function return type on. and explicit any is disabled. so I need to do something about the return type
this doesnt work either
next marlin
i don't see how that's relevant
export const getModels = (): (new () => Model)[] => [UserDetail];
wow.. why does that work?
UserDetail is extending model yes but new Userdetail will give instance of userdetail not model. so why does this work and not the generic?
the generic logically sounds more accurate. T extends Model and new() returns instance of T.
next marlin
your function just isn't meant to be generic
generic functions are functions that have unknown typings, where multiple arguments need to follow the same unknown type, or the return type has a type related to an argument
lilac rampart
Hm ok. Understood that part. Just wondering why new()=>Model is a correct type for class extending Model.
next marlin
for generics in methods, if the generic is only used once, it's likely a mistake to use the generic.
next marlin
Hm ok. Understood that part. Just wondering why new()=>Model is a correct type f...
why wouldn't it be? you used that exact type in the generic