Learn Relay – A comprehensive introduction to Relay and GraphQL
learnrelay.org
learnrelay.org
This is a great initiative! I remember struggling to learn Relay, I love it though, used it in some toy apps and will use it in some upcoming projects that I have. However I have a few issues with Relay: the main one is that it overall discourages people from starting with GraphQL. From creating a Relay-compliant GraphQL server to adding it to your app, Relay forces you to good conventions that, unfortunately, requires you to learn about its concepts and makes it super difficult to ramp up fast.
For anyone interested in working with Relay and GraphQL in general, I would advise you to start first with just learning GraphQL, without Relay and its constraints. You'll see that much of the issues you may have with GraphQL may come from actually trying to comply to Relay. Once you are okay with GraphQL, then, you can move to learning Relay.
Finally, I want to insist on the fact that GraphQL is just a specified language that can be consumed by any client you need/want. Relay is made by Facebook, for Facebook, which is a cool thing but may be a bit too much for your simple app or may not be adapted if you are migrating a legacy app to GraphQL (which was my case). That's why you should take a look to alternative clients as well (Apollo [0] for instance ;-) )!
One important thing to note here, is that Relay and Apollo are taking different approaches. Relay provides a great framework which works excellent for a lot of use cases and provides the most convenient and robust solution for that. In some cases you want to "break out" of that framework and be more in control how data is fetched or mutated. In that case Apollo is a fantastic choice as well. Especially in combination with Redux. Fun fact: We're actually using both - Relay AND Apollo - in our dashboard at Graphcool. Feel free to take a look at the source here: https://github.com/graphcool/dashboard
On a side note: We're already working on a similar project but focussed on Apollo. If you're interested in getting involved, we're still looking for collaborators: https://github.com/learnapollo
learnapollo seems awesome too! I think that Apollo would benefit from this kind of documentation. You should definitely come and send a link on the Apollo's slack!
In general Graphcool is a great idea if you want to start fast with GraphQL (with any client).
We found it to be very difficult to get started with Relay. At Graphcool we are building the dashboard, a core component of our product with Relay, so we had to become experts. Now we have turned this into (what we hope to be) a compelling getting started tutorial.
We would love to get some feedback, and if you have any questions about Relay or GraphQL in general I'm happy to answer. :)
Have you also seen the integrated GraphiQL and data browser?
When thinking about building a GraphQL entry point there are 3 main areas you will have to consider: Performance, Authorization and Complexity.
GraphQL is designed to be backed by arbitrary storage, so it would actually be feasible to have a bunch of GraphQL resolve functions that just call out to existing REST endpoints. To make this performant you need to implement a proper batching mechanism like DataLoader in node or Sangrias Deferred Resolver. If your existing api has automatically generated docs in a format like swagger you might even be able to generate the entire GraphQL schema from this :-)
On a side note: We're already working on a similar project but focussed on Apollo. If you're interested in getting involved, we're still looking for collaborators: https://github.com/learnapollo
I also found Relay a nightmare to understand. Everything is overcomplicated and messy, which is probably why they're talking about Relay 2.0 already. I was a bit frustrated when I found that this blog post was the most helpful piece of information I could find on Relay, and it tells you to just use FIELDS_CHANGE everywhere and ignore the rest of the mutation config features: http://blog.pathgather.com/blog/a-beginners-guide-to-relay-m... .
Some things that make Relay frustrating:
* Pointless restrictions on what you're allowed to do at the "root" require you to do everything under a "viewer" subnode instead.
* Relay "Routers" are completely pointless and should be removed.
* Mutation configs are totally confusing, and they're tightly coupled to the server-side implementation of the mutation. We have a compile step where the client inspects the schema that was generated by the server. Why can't we generate the mutation configs as well? I know there's probably not enough declarative information readily available, but there should be.
* Relay mutations are only allowed to have one input field and one output field in the GraphQL definition. This is a pointless incompatibility between Relay and non-Relay GraphQL endpoints.
Falcor also exists, and is much simpler, though it has its upsides and downsides:
* You're not allowed to pass any arguments other than the standard from/to pagination arguments. Want to implement faceted search? Too bad. It's "Not a querying language", for some reason.
* It has something called "calls" which are basically the same thing as Relay's mutations but you have a little less control over how cache invalidation is handled than you do with mutation configs. There's no RANGE_ADD, for example. To add/remove items in a list you have to invalidate the entire list. Maybe that's OK though? But it sure is annoying if you're trying to move an item from one list to another on the client side and don't need to wait for the server to catch up.
* No built-in support for optimistic updates yet.
One thing I see in common between React and Falcor is they are both rather complex ways to collaborate with yourself while ignoring events from the outside world. In other words, it's a lot of work to not have pubsub. I guess this is because pubsub doesn't scale? But in the mean time, I'm tempted to play around with Horizon instead.
It includes features like optimistic UI, easy ways to invalidate cache after mutations, arbitrary pagination models, and more.
(Disclaimer: I work on Apollo)
Fortunately, this guide links to a tutorial on that too: https://learngraphql.com/basics/introduction
In contrast, for a newer project I used Apollo and was up and running in no time at all. It's very easy to reason about, but also gives you great React integrations.
We have since moved to Redux and are going to back out Relay from the application we used it in. With all of Redux's issues (ceremony, boilerplate, etc) it provides a standard model for us to reason about, and a decoupling of data retrieval from presentation.
Quite the opposite. Relay allows you to write proper presentation components and then wrap them in data-provider components. This is a step toward isolation of presentation and data management. If you could move all methods that actually manipulate the data up out of the presentation components and into their wrappers, that's even better.
Unfortunately, the parent component has to reference the wrapper instead of the wrapped component, so you get this alternation between presentation and data management. But at least the leaf nodes can be considered reusable presentation components with no coupling to the data layer.
Anyway, everyone is doing this these days. Check out:
We decided very early on to use Relay for our main frontend (a dashboard similar in complexity to Parse.) It's probably one of the largest open source projects using relay atm, so maybe having a look at that can be helpful https://github.com/graphcool/dashboard
In summary we have found that the benefits Relay offer makes up for the quirks and complexity Relay currently forces you to learn. Hopefully Learn Relay can help more people get up to speed faster.
My weekend is packed already, but I'll be back to check this out. I'm just starting to take a second look at GraphQL and co. Last time I looked at it, the conclusion was "extremely interesting, but too alpha for work."
Did you notice that Facebook's ad / business manager uses a mix of GraphQL, REST, and RPC over HTTP POST? Watching the traffic in major production applications is fascinating.
We'd be more than happy to share some insights on what we've learned while building Graphcool. The best way going forward will be following our blog: https://blog.graph.cool/
Also, feel free to join our Slack in case you have any questions: https://slack.graph.cool/