Cannot subclass Loader

[ulrikdem]

Loader.prototype.constructor is not correctly set, which means that a super call from a subclass constructor does not call the Loader constructor (see 26.3.1).

[briandipalma]

I thought Loader was a factory and that you didn't subclass it, you created instances of your own Loader by passing in arguments for the Loader hooks you wish to override. Is that now how System is meant to work in the browser?

[ulrikdem]

The spec says the following:

The Reflect.Loader constructor is designed to be subclassable. It may be used as the value in an extends clause of a class definition. Subclass constructors that intend to support the specified Loader behaviour must include a super call to Reflect.Loader.

I guess whether you create an instance of Loader or create a subclass depends on what you want in the specific situation.

[briandipalma]

@ulrikdem Cool thanks for clarifying that, I didn't realize that. I had a vague memory that you were meant to pass in the hooks you wanted to override and a new Loader instance will be returned to you but I must have been mistaken.

[ulrikdem]

The Loader constructor takes an options object as argument. The options object can contain hook functions, so that works as well.

[briandipalma]

Right, I thought that was meant to be the way of creating Loader instances, hence why you couldn't subclass it. It looks like that not the case though.

[guybedford]

@ulrikdem thanks for the PR. Can you help me understand why the constructor needs to be explicitly set on the prototype for classes to work? I thought having the constructor automatically set on the instance was enough for super to work out?

[guybedford]

Ok got it... overriding instead of extending the prototype removes the default constructor setting! Looks great to me then.