Is it possible to call an async function inside a constructor in react-native?

Question

I have an async function named async a() which has to be run before function componentDidMount().

So how can I call an async function inside a constructor? Because the constructor function gets run before the componentDidMount function.

I need to be sure my async a() completes first in the constructor and then all methods within componentDidMount are executed.

Answer 1

You can't do it inside constructor, because constructor can't wait for await
So you can have another function(for example b()) for all the processes you want to run after async a(). And you have two choice for doing this:

1- use async/await:

async componentDidMount() {  
    try {
      await a();  // it will wait here untill function a finishes
    } catch(err) {}

    b(); // after function a finished, this function will calls
}

2- using .finally:

componentDidMount() {
    // in below line, function `a` will call, and when it finishes, the function inside `.finally` will be notified
    a().finally(() => {
        b(); // now your function `a` finished and you can call extra process in function `b`
    });
}