Does your Flutter app talk to a backend or server-side API?
Then it pays off to separate the UI code from your data-access layer.
Here are my tips to make your client code backend-agnostic. 🤔
Thread. 🧵
First of all, what does backend-agnostic mean?
Whether your app talks to a REST API or a remote database like Cloud Firestore, you don't want any of the data-access code to be mixed up with the UI.
Instead, put it into a separate data layer.
A very good way to do this is to use the repository pattern.
This lets you encapsulate all the data access logic (serialization, networking) inside a class.
And the rest of the app can talk to the public interface of that repository.
The repository pattern has several advantages:
- if the API changes, you only need to update the code in the repository
- your code becomes more testable (you can use a mock repository in your tests)
- migrating to a different backend becomes easier
This means that any UI code (or provider) that calls the jobsQuery() method will also depend on cloud_firestore.
So how can we prevent "leaky" abstractions?
The only way is to ensure that the public interface of the repository does not expose any Firebase-specific APIs.
Using the same example, this can be done by returning a Stream<List<Job>> rather than a Query<Job>.
But is that worthwhile?
After all, working with Query makes it easier to support pagination (with the firebase_ui_firestore package).
But if we work with streams directly, we have to do more work and implement pagination ourselves (not an easy task).
So when considering which abstractions to add, always weigh the pros and cons:
Moving the data-access code into a repository? ✅ Worth it (more testable and maintainable code)
Replace Query<Job> with Stream<List<Job>?
❌ Maybe not (more work to implement pagination)
Also note: different backends offer different features 👇
- Firebase gives you realtime listeners, caching, and offline mode
- But a simple REST API won't
So don't go for the lowest common denominator "because of abstraction".
Make the most of what your backend has to offer.
Choosing the right abstractions can be challenging.
If for a deeper dive into this topic, read this article:
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