Incorporating TypeScript 3.7, I created an interface featuring a property designed to accept a constructor function:
interface IConstruct<T> {
type: new (...args:ConstructorParameters<T>) => T;
}
I initially assumed that IConstruct<User> would include a property {type: User}.
However, the compiler is indicating that T cannot be utilized in this context. What is the reason for this error message?
TS2344: Type T does not satisfy the constraint 'new (...args: any) => any'
In the case of ConstructorParameters, the structure appears as follows:
type ConstructorParameters<T extends new (...args: any) => any> =
T extends new (...args: infer P) => any ? P : never;
Therefore, the type parameter T must be an extension of a constructor function defined by the constraint
extends new (...args: any) => anyclass User {
constructor(public name: string) { }
}
// include constructor function type constraint for T
interface IConstruct<T extends new (...args: any) => any> {
// InstanceType can be used to infer instance type from class type
type: new (...args: ConstructorParameters<T>) => InstanceType<T>;
}
type UserConstruct = IConstruct<typeof User>
const constr: UserConstruct = {
type: User
}
constr.type // new (name: string) => User
const userInstance = new constr.type("John") // userInstance: User
console.log(userInstance.name) // John
The issue has been successfully resolved: https://github.com/microsoft/TypeScript/issues/31278
Personally, I found that the missing typeof was causing the problem:
class Parent<T> {
constructor(readonly data: T) {
}
}
class Child<T> extends Parent<T> {
constructor(...args: ConstructorParameters<typeof Parent<T>>) {
super(...args);
}
}
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