CODEWITHSUNDEEP
javascriptclassecmascript-6
Rob Evans
Rob Evans

Reputation: 6968

JavaScript ES6 Call to "super" After Async Call

When using ECMAScript 6 and classes, is it possible to call the super class method from an extending class method after an async call has completed?

Here is an abstract of the question in code:

class Foo {
    constructor () {

    }

    myMethod (data) {
        console.log('Data was: ', data);
    }
}

class Bar extends Foo {
    constructor () {
        super();
    }

    myMethod () {
        database.getDataForId('wth4308g40giemwfo', function (err, data) {
            super.myMethod(data);
        });
    }
}

Using the above class Foo.myMethod() will result in an error because super no longer refers to the superclass of Foo and is undefined inside the callback.

I have tried to keep a reference to super before the callback and use that reference in the callback after it completes but that doesn't seem to work e.g.:

myMethod () {
    var mySuper = super;

    database.getDataForId('wth4308g40giemwfo', function (err, data) {
        mySuper.myMethod(data);
    });
}

Is it possible?

Upvotes: 3

Views: 923

Answers (2)

CodingIntrigue
CodingIntrigue

Reputation: 78545

Arrow functions will preserve all lexical references, not just this, so you can use one to access super too:

myMethod () {
    database.getDataForId('wth4308g40giemwfo', (err, data) => {
        super.myMethod(data);
    });
}

Upvotes: 6

madox2
madox2

Reputation: 51861

You cannot hold reference to super but you can to the function:

myMethod () {
    var myMethod = super.myMethod;
    var self = this;

    database.getDataForId('wth4308g40giemwfo', function (err, data) {
        myMethod.call(self, data);
    });
}

Upvotes: 2

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