Re: how to defer a method call until the return of an async server call?

Somewhat depends on the concrete case, there is probably not the one solution that always fits.

1.) Dependency Inject: Load the list externally, e.g. new InvitationForm(users). As setInviter() depends on the list its not a good idea to use invitationForm.setUsers() because then you still need to call them in the correct order.

2.) Observer pattern: Use EventBus or invitationForm.addUsersLoadedHandler() depending on the separation you want

3.) "Replay" method call: remember the fact that setInviter() has been called and do the actual work once the users list is loaded. This can be annoying to write if you have multiple methods that depend on the users list.

4.) Distinct load() method with callback: Introduce InvitationForm.loadUsers(new Callback<S, F> callback() {}); and call it externally. S is the type for onSuccess, F for onFailure. Both can be Void if you are not interested in them.

5.) Refactor code so that an inviter does not depend on the list of users he/she can invite. I would understand if the list of users depends on the inviter (because the users are friends or similar of the inviter) but the other way around sounds strange to me.

Personally I have never done 3.) so far.

I would always start with 5.) and then if the InvitationForm isn't widely used probably 1.). If the form is used in multiple areas I would stick to 2) or 4). In case of 2.) I would use EventBus if parties that are interested in this information might be "far away" from the InvitationForm. If only the parent is interested in this information the addUsersLoadedHandler() approach makes more sense to me.

-- J.

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