如何在Angular 2中从另一个Promise函数调用一个Promise函数？

Question

I have one function that returns a Promise that needs to call another function that returns a Promise:

getUser(): Promise<User> {
    this.getAPIUser().then(result => {
        ..Do some stuff with result..
        return Promise.resolve(result);  // This doesn't work
    });
}

getAPIUser(): Promise<User> {
    return Promise.resolve({ firstName: 'Jason' });
}

I think this doesn't work since the getUser "return Promise.resolve" is in the context of the getAPIUser then handler. This was really easy in Angular 1, you would just instantiate a $q object and then resolve that object wherever you needed it. I can't figure out what the equivalent is in Angular 2/Typescript/EM6.

Any help would be appreciated.

Answer 1

Your getUser method doesn't return a promise at all.
When you invoke the then method on a promise it returns a Promise back and that is what your method needs to return:

getUser(): Promise<User> {
    return this.getAPIUser().then(result => {
        ..Do some stuff with result..
        return result;
    });
}

Answer 2

For the sake of completeness this works as well:

getUser(): Promise<User> {
    return new Promise((resolve) => {
        this.getAPIUser().then(user => {
            resolve(user);
        })
    });
}