What are the benefits and drawbacks of using event aggregators for viewmodel communication?

1 What is an event aggregator?

An event aggregator is a design pattern that decouples the components of a system by using a central mediator that handles the events. In MVVM, an event aggregator can be used to facilitate the communication between viewmodels that are not directly related or share a common parent. For example, if you have a viewmodel for a dashboard that displays various widgets, each widget can have its own viewmodel that publishes events to the event aggregator when something changes. The dashboard viewmodel can then subscribe to those events and update the view accordingly.

2 What are the benefits of using event aggregators?

Using event aggregators in your MVVM application can offer several advantages, such as loose coupling, flexibility, and scalability. With events instead of direct references, you can reduce dependencies and coupling between viewmodels, allowing for greater modularity, testability, and maintainability. Moreover, events provide the ability to add, remove, or change viewmodels without affecting the rest of the system. Events also enable the reuse of viewmodels in different contexts or scenarios, as well as the ability to handle complex scenarios where multiple viewmodels need to communicate with each other or external services. Finally, events can be used to implement cross-cutting concerns such as logging, error handling, or notifications.

4 How to use event aggregators in MVVM?

If you decide to use event aggregators in your MVVM application, it's important to follow certain best practices and guidelines. Choose an appropriate library or framework for your platform and language, such as Prism, Caliburn.Micro, or ReactiveUI in C#, or Backbone, Angular, or Vue in JavaScript. Define clear and consistent event types and payloads that convey their purpose and data. Use descriptive and meaningful names for events and viewmodels, and follow the principle of least privilege by subscribing only to the events you need. When you no longer need them or when your viewmodel is disposed, unsubscribe from the events to avoid leaking memory or resources. Finally, use proper error handling and logging mechanisms to deal with exceptions or failures that might occur during event communication.

5 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?