Here, we’ll be exploring Apollo Client, Relay, and URQL, as well as each of their pros and cons, to help you make the right choice when selecting a GraphQL client for your future projects. Let’s explore implementations of these three Relay conventions directly on our GraphQL server. Then later in the chapter we’ll implement them in our client app. Our GraphQL server defines our GraphQL schema and how to resolve queries against that schema. For the most part, it doesn’t dictate what the structure of your schema should be.
So, even if we define another fragment, BlogPostAuthor_blogPost, which selects the title and coverImgUrl, we don’t receive access to them unless we ask for them in the same fragment. This is enforced by Relay’s type system both at compile time and at runtime. This safety feature of Relay makes it impossible for components to depend on data they do not explicitly select. So, developers can refactor the components without risking other components. To reiterate, all components and their data dependencies are self-contained.
FromGlobalId takes the “global ID” created by toGlobalID, and returns the type name and ID used to create it. This library is designed to work with the GraphQL.js reference implementation of a GraphQL server. A basic understanding of CSS Entities GraphQL and of the GraphQL.js implementation is needed to provide context for this library. This is a library to allow the easy creation of Relay-compliant servers using the GraphQL.js reference implementation of a GraphQL server.
Now, inside our src folder, we are going to create a new file called relay. Inside this file, we are going to create our Relay environment. When creating a new React app that’s going to use a GraphQL API, having a nice GraphQL client that can help scale and keep the app performant at the same time makes a big difference. The open source project relay-hooks allowed the community to experiment with Relay and React Hooks, and was a source of valuable feedback for us.
- URQL supports document caching for content-heavy pages and normalized caching for dynamic and data-heavy applications.
- We partner with companies to design, develop, and scale their products.
- So, even if we define another fragment, BlogPostAuthor_blogPost, which selects the title and coverImgUrl, we don’t receive access to them unless we ask for them in the same fragment.
- Our overarching goal is to enable developers to create correct, high-performance applications in a straightforward and obvious way.
Our query is going to be named PodcastsQuery, and we are going to pass a fragment inside it. Inside our Podcasts file, we will use the usePreloadedQuery to query a list of podcasts. Another big difference is that you don’t to pass your Relay environment to useLazyLoadQuery like QueryRenderer did.
It allows developers to declare what data each component needs via GraphQL, and then aggregate these dependencies and efficiently fetch the data in fewer round trips. In this guide we’ll introduce the key concepts for using Relay in a React app one at a time. Relay was born out of our Best Cloud Security Companies List of Top 10 Cloud Security Providers experiences building large applications at Facebook. Our overarching goal is to enable developers to create correct, high-performance applications in a straightforward and obvious way. The design enables even large teams to make changes with a high degree of isolation and confidence.
Relay removes the responsibility of developers to route the data down from query to the components that need it. There is no way for a component to accidentally or deliberately depend on data that it should be just passing down in the component tree if it cannot access it. All the hard work is taken care of by the Relay framework if we follow the conventions discussed. We still have a query that is sent to the GraphQL server and the data is fetched and stored in the Relay data store. The Relay compiler takes all the declared fragments in the codebase and generates the type files, which can then be used to annotate a particular component. Now, let’s look at an example of components in a single post of a blog application.
Once the app was released to the iOS and Android app stores, we wanted to revisit that choice, and look at how Relay could work with our app. We’re looking for talented developers who are passionate about new emerging technologies. The Example App is a more sophisticated version of what we’ve started building here.
Querying data with URQL
Any view can read from and write to any model–and with auto-binding, models could write to other views, which in turn will do their own writing. This back-and-forth flow could cause a cascading update, and while it can be avoided with good code, the idea of things going in multiple directions is scary. The solution is in verifiable constraints; having Custom Cypress Command Examples Cypress Testing Tools an enforced one-way flow is the smart alternative. Anywhere in the application, you know that there’s only one direction to go. The Flux pattern is an attempt to explore this idea, and it works like a charm. Angular.js has been theMVC framework of choice for top developers for years now but, thanks to Facebook engineers, this is changing in 2015.
Now we are going to import our PodcastsResults components and pass it inside the Suspense component. The RelayEnvironmentProvider is used for setting Relay to a React Context. The recommendation here is to always use a single instance of this components, at the root of your app. After creating our Relay environment, we are going to pass it inside our index file. We need to import the RelayEnvironmentProvider and pass our Environment as an environment.
Open source plans
This table provides a quick overview of the three GraphQL clients, along with some of their noteworthy features. Run your code and inspect the network tab to check the result object. We then specify our query data by passing the query string to the client.query() method, as shown below. First, install the URQL library from within your React application.
We’ve installed the GraphQL GUI tool “GraphiQL” on this demo server. Each component specifies what it needs and Relay figures out if there’s any duplication, before making the query. Relay will aggregate the queries, process the responses, and then hand back to each component just the data it asked for.
Each component specifies its own data dependencies declaratively using a query language called GraphQL. The data is made available to the component via properties on this.props. Using Global Object Identification, Relay is capable of automatically merging mutation updates for any affected objects, and updating only the affected components. Later, you can read the data from the store in a functional React component by calling the usePreloadedQuery hook. Let’s assume the response will eventually be JSON (it doesn’t need to be, but we’re not scratching that standard yet); a JSON will be a set of keys and values .
Configure the Relay Compiler
In order to start using Relay, we need to install a few dependencies. It has support for React Hooks and it’s very powerful and easy to use. One more neat little tidbit, if you are trying to access a nested type within a GraphQL query type, you can use a Flow Utility Type, $PropertyType to assign the nested type to a property. I know it’s a lot to wrap your head around, but the important item that relates to what we are discussing comes in the next paragraph from the documentation I quoted above. Once npm run build has run, you may import or require() directly from node. PluralIdentifyingRootField creates a field that accepts a list of non-ID identifiers and maps them to their corresponding objects.
When building a schema for GraphQL.js, the provided library functions can be used to simplify the creation of Relay patterns. An overview of the functionality that a Relay-compliant GraphQL server should provide is in the GraphQL Relay Specification on the Relay website. That overview describes a simple set of examples that exist as tests in this repository.
In the meantime, we’ll be providing more and more information in the form of blog posts . As we get closer to the open source release, you can expect more concrete details, syntax and API descriptions and more. The rest of the schema that represents the actual API will then be generated for you.