Inherited Constructors execute before sub class field initializations

[arciisine]

TypeScript Version: 2.1.5

Code

class Base {
  id:string;

  constructor(config:any) { 
      // Given a defined schema object, bind the inbound config to the current 
      //   instance, enforcing types and discarding unused fields
      bindToSchema(ObjectSchemaRegistry.get(this.constructor), this, config);
  }
}

class SubType extends Base {
   name:string = 'basic';
}

Expected behavior:
new SubType({ name : 'test' }).name == 'test'

Actual behavior:
new SubType({ name : 'test' }).name == 'basic'

The sub class field initialization executes after the base class constructor executes. I'm not sure if this is 100% desirable but I can understand the reasoning for it. If this is unchangeable, I would look for some way to execute the bindToSchema function after the sub class field initialization has occurred (barring making every use of the constructors call bindToSchema manually).

[vladima]

duplicate of #10634?

[arciisine]

Sounds like it, didn't come up in my search. Is there any way to achieve this functionality (calling code after the constructors finish) without changing the order of construction?

[RyanCavanaugh]

Nope. General pattern here is to have some convention like calling this.init() after super in the derived class constructors.

[arciisine]

Understood, it just seems like an anti-pattern to have, what is essentially, a secondary constructor to compensate for the initialization of fields.

I'm toying with using an inherited static method to act as the constructor (e.g. Sub.new, or Sub.from), but I'm not sure if relying on inheritance for static members is a good idea either.

[arciisine]

So, playing around with some solutions, what I'm looking at is:

class BaseSchema {
  static new<T>(this: new () => T, data: any): T {
    return BindUtil.bindSchema(this, new this(), data);
  }
}

This then allows for

class Person extends BaseSchema {
  name: string = 'bob';
}

let person:Person = Person.new({});