Looking to convert this Typescript method into one that returns a Promise, but only once the
this.user.currentCourseId = student.currentCourseId;Is it feasible to achieve this?
public getUserData()
{
...
this.authState.auth.getToken().then(token =>
{
this.user.token = token;
this.userService.update(this.user).then(student =>
{
this.user.currentCourseId = student.currentCourseId;
});
});
}
It's important to note, as highlighted by jfriend, that you cannot delay returning a promise until it is complete. This would be like getting ahead of yourself. Instead, return the promise immediately and then chain off of it to wait for its fulfillment.
Additionally, I'd like to emphasize the usefulness of promise chaining in order to steer clear of falling into the trap known as the "tower of doom":
public fetchUserData()
{
...
// return promise from function
return this.authState.auth.getAccess().then(token =>
{
this.user.token = token;
// return another promise here to continue the chain
return this.userService.update(this.user)
}).then(student => {
this.user.currentCourseId = student.currentCourseId;
});;
}
fetchUserData().then(() => {
// currentCourseId has now been updated
});
By immediately returning the promise, any subsequent promises inside the initial .then() handler are chained to the original promise:
public fetchUserData()
{
...
// return promise from function
return this.authService.getCurrentUser().then(token =>
{
this.user.token = token;
// additional promise returned here to continue chaining
return this.dataService.updateUser(this.user).then(student =>
{
this.user.currentCourseId = student.currentCourseId;
});
});
}
// implementation
fetchUserData().then(() => {
// access values set within promises
});
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