Unlock the Power of Modular GraphQL Applications
What Are GraphQL Modules?
GraphQL Modules is a revolutionary approach to building scalable, maintainable, and testable GraphQL applications. By breaking down your application into smaller, independent modules, you can create reusable code that’s easier to write, test, and maintain. GraphQL Modules helps you implement the separation of concerns design pattern, allowing you to focus on individual features without worrying about the complexity of your schema and resolvers.
The Benefits of GraphQL Modules
So, why do developers choose GraphQL Modules? The answer lies in its numerous benefits, including:
- Reusable modules: Define your GraphQL schema in smaller pieces, making it easy to move and reuse code.
- Scalable structure: Clearly defined boundaries make it easier to manage multiple teams, features, microservices, and servers.
- Clear path to growth: Separate features into modules, making it easy to scale from simple, single-file modules to complex, multi-file, multi-team, and multi-server modules.
- Testability: Testing small pieces of code is easier than testing larger chunks, and GraphQL Modules provides a rich toolset for testing and mocking your application.
How GraphQL Modules Work
Let’s take a closer look at how GraphQL Modules work using a simple library application. We’ll break down the application into Book, Author, and Genre modules, each composed of type definitions and resolver functions.
Creating a GraphQL Module
To get started with GraphQL Modules, you’ll need to install the package and GraphQL. Then, use the createModule function to create a module, adding a unique ID and optional dirname to help locate issues in your type definition.
Type Definitions and Resolvers
GraphQL Modules uses Schema Definition Language (SDL) to define schemas, just like GraphQL Schema. Resolvers are implemented in the same manner as any other GraphQL implementation. Modules created by GraphQL Modules can detect duplicate, incorrect, or old resolvers.
Merging Schemas with GraphQL Modules
Each module contributes to a small part of the entire schema. To merge the schemas together, create an application using GraphQL Modules’ createApplication. Then, use the createSchemaForApollo function to get a schema adapted for Apollo Server.
GraphQL Context and Dependency Injection
In GraphQL, the context argument is shared across all resolvers executing for a particular operation. You can use context to share per-operation state, including authentication data and dataloader instances. GraphQL Modules supports dependency injection, making it easy to separate business logic from resolvers and make services available to resolvers.
Dependency Injection Providers
There are three types of providers: class providers, value providers, and factory providers. Class providers create an instance of a class and make it available to the injector. Value providers provide a ready-to-use value. Factory providers are functions that provide a value dynamically based on application state.
GraphQL Scopes
Each token or provider has a scope that defines its lifecycle. Scope can be either singleton or operation. Singleton providers are created once and live throughout the application’s lifecycle. Operation providers are created per execution context or for each GraphQL operation.
Getting Started with GraphQL Modules
With GraphQL Modules, you can create maintainable, scalable code that’s easy to write, test, and maintain. By separating your code into smaller, independent modules, you can focus on individual features without worrying about the complexity of your schema and resolvers. Now that you know the basics, it’s time to dive deeper into advanced concepts like subscription, middleware, execution context, and lifecycle hooks.