Graphql codegen

This is a very powerful feature that allows you to write your code in a type-safe manner, without you needing to manually write any types for your API calls. To do this, graphql codegen, we will use Graphql Code Generator.

GraphQL uses a type system to clearly define the available data for each type and field in a GraphQL schema. Type generation libraries can take advantage of the strongly-typed nature of a GraphQL schema to automatically generate TypeScript types based on that schema. You can use these generated TS types in your resolvers to type-check that your resolvers' return values match the field types dictated by your schema. Type checking your resolvers enables you to catch errors quickly and gives you the peace of mind that type safety ensures. Looking to generate types for your Apollo Federation subgraphs? Our Subgraph template lays down the groundwork so you can quickly set up a subgraph with generated types.

Graphql codegen

There's one important step that we need to take care of before proceeding with our TypeScript app - we need to generate the TypeScript types to represent all of the GraphQL types in our schema! But because we're going to be writing queries for Track and Author data, we need the frontend to understand what type of data they involve. We could write out the TypeScript types manually— we know that a Track has text for a title , and an Author has text for a name , and so on—but if we change our schema in the future, we have to remember to update our frontend as well; this means that our frontend's TypeScript types can easily get out of sync, if we're not careful! Instead, we can look to the GraphQL API's schema as the "single source of truth" for all of the types we could possibly query on the frontend. An easy way to do this, and to keep our frontend's type definitions consistent with the backend, is to use a GraphQL Code Generator. As we work on new features, we'll benefit from the clarity TypeScript gives us about what data exists on each type and what kinds of operations can be performed on it. Here's how the process works. Ready to get started? Let's go! We only need these packages during development, so we'll install them under devDependencies. If we run the command right away with npm run generate , we'll see that we get an error—this is because we haven't yet created the codegen. Let's define codegen. This file should contain a number of instructions that tell the GraphQL Code Generator what we want it to do, such as:. We'll start by creating a new object called config and exporting it.

See options.

It'll allow you to generate Dart serializers and client helpers with minimal config. The framework makes no assumption on how you structure your fragments or queries, for each operation. Read more about the tool and motivation at the GraphQL Codegen deep-dive and on how you can structure your flutter apps with the tool on Structure your Flutter GraphQL apps. The framework does not fetch your schema for you, so before you run this, you'll need to add your schema to your project. See options. Will be inside HookWidgets.

In schema-first, you write. Now, if you are using Typescript, you might find yourself having to write types again for other purposes - your resolvers for example. That can quickly become a problem, not only because it feels like a waste of time, but also because it makes it hard to maintain. If your codebase and your schema grow in complexity, and you have a whole team working on it, a small type definition update can cause a huge mess! If we look at a fullstack Typescript application, we have to duplicate our type definitions at least 3 times:. Now imagine if, 4 months later, we want to add tags to our posts. We would have to go through the same 4 steps to update the types! But with GraphQL codegen, we have one single source of truth the schema file! Checkout the repo for more details. We can bootstrap a React project with Typescript very easily thanks to the Create-React-App template:.

Graphql codegen

Because GraphQL is a communication pattern, there are many tools to help you get started working which support GraphQL in all sorts of languages. Depending on your deployment target, you may need to use an additional library. See the documentation for further details. Mercurius is a flexible and extendible GraphQL adapter for Fastify, a blazing-fast web framework with the least overhead and a powerful plugin architecture. An extensible GraphQL server with modules for caching, request parsing, debugging, subscriptions and more The example below installs and initializes the GraphQLBox server with a persisted cache and debugging enabled. A highly customizable and versatile GraphQL client with which you add on features like normalized caching as you grow. It's built to be highly customisable and versatile so you can take it from getting started with your first GraphQL project all the way to building complex apps and experimenting with GraphQL clients.

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We can do this by setting an additional property below preset called presetConfig. You can try this tool live on your browser and see some useful examples. Used by This is done by specifying the fallbackEnumValue option on the enum. Next, we'll install the packages we need to generate types automatically based on our schema. You can select an existing enum value to be the fallback enum value. Don't have one? Allows custom enum implementation. So why don't we just tell the GraphQL Code Generator to reference the types in the server folder's schema? GraphQL Code Generator lets you choose the output that you need, based on plugins , which are very flexible and customizable. In the file where you create your server, you can read in your schema using readFileSync from the fs package:. For example:. You can add new mappings for your custom scalars or overwrite existing configurations. For instance: Given schema. With the query from above: person.

Don says that good design is primarily discoverability and feedback. For example, when you encounter something new like, a new codebase , how quickly can you discover what you can do discoverability?

You can pass your exported context interface to the contextType configuration option, like so:. In the file where you create your server, you can read in your schema using readFileSync from the fs package:. All of our code is contained in the src folder, and we want to be sure that it looks for files in all of the src subfolders as well! You can try this tool live on your browser and see some useful examples. Running npm run generate will still produce an error, but we'll take care of that in the next lesson by adding our first GraphQL operation! See the entire codegen. As we work on new features, we'll benefit from the clarity TypeScript gives us about what data exists on each type and what kinds of operations can be performed on it. In other words - why are we going out to the GraphQL endpoint to gather this information? Finally, we'll check out the types it generated for us! Recall that on the server side, we used the tagged template literal gql from the graphql-tag library to prepare our GraphQL strings. Within the config object, we'll define three properties: schema , documents , and generates.