Isn't it always the case that `Promise.resolve()` returns an immediately
resolved Promise? That means that the `.then` clause would get executed
immediately as well, which is before you have a chance to set `this.foo`.
Seems like what you need to do is something more like this:
```js
// class Foo
constructor() {
(new Promise((resolve, reject) => { setTimeout(() => { resolve(); },1);
})).then(() => {
this.methodThatSubclassOverrides()
})
}
```
Done this way, the call to `resolve()` will be thrown onto the run loop for
execution later.
On Sat, Jul 27, 2019 at 8:57 PM #!/JoePea <[email protected]> wrote:
> I feel like I'm going crazy, but I have a class hierarchy, and one of
> the constructors in the hierarchy defers some logic to a microtask,
>
> ```js
> // class Foo
> constructor() {
> Promise.resolve().then(() => {
> this.methodThatSubclassOverrides()
> })
> }
>
> methodThatSubclassOverrides() {}
> ```
>
> and in the subclass there is
>
> ```js
> // class Bar extends Foo
> constructor() {
> super()
> this.foo = 123
> }
>
> methodThatSubclassOverrides() {
> console.log(this.foo) // should be "123"
> }
> ```
>
> You'd think the output should be "123" because the deferred code will
> run after construction is complete.
>
> However, in my current project, the promise deferral seems to run
> before the construction returns to the Bar constructor, thus this.foo
> is not set, and calls `methodThatSubclassOverrides` before the Bar
> class has a chance to run `this.foo = 123`. So the result of the
> console.log is "undefined".
>
> It is totally weird. Do Promises ever resolve before a constructor
> stack finishes?
>
> I don't have a simple reproduction at the moment.
>
> - Joe
> _______________________________________________
> es-discuss mailing list
> [email protected]
> https://mail.mozilla.org/listinfo/es-discuss
>
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