This article was published on Monday, January 7, 2019 by Arda Tanrikulu @ The Guild Blog
TL;DR: If you are writing a large-scale project, it's necessary to understand the relations
between your pieces of code, and how they effect each other. Otherwise, it might be difficult to
deal with changes later.
While developing a large-scale project, removing, changing and modifying parts of the project
can become a very time-consuming and risky task, because understanding the full side-effects of
those changes is very hard.
In GraphQL-Modules, you can declare your modules in a feature-based
structure, with clear enforced boundaries and avoid unexpected side-effects during development.
Each module can declare its own scope of the complete schema:
Each module has its own schema, context, typeDefs, resolvers, and
business-logic and each module is encapsulated, which limits the module's access to only its own
parts of the schema.
So, what's the real benefit of this?
Let's assume you have an authentication module;
After a while, you decided to use AccountsJS in your GraphQL project which has
completely different implementation than the existing one.
This can be a risky change, because you're afraid of breaking a lot of things, and you can't be sure
about the all the places in your code that uses values affected by the authentication module, for
example the global context.
With GraphQL-Modules' approach of encapsulation, even the context is completely encapsulated, so
every module that uses your existing AuthenticationModule's context in defined on the
imports of the dependent modules, and its interface is already extended by
AuthenticationModule's context if you're using TypeScript. When it is removed, you
will notice that change on compile-time immediately.
Let's take a look at some code, to show how GraphQL Modules makes you create those dependencies
explicitly.
AppModule is our top Application Module;
import { GraphQLModule } from '@graphql-modules/core'
import { AuthenticationModule } from './modules/auth.module'
const AppModule = new GraphQLModule({
imports: [
AuthenticationModule, //this module has `user` in its context
SomeImportantModuleThatUsesAuthenticatedContext
// ...
]
})
And there is another module that tries to use AuthenticationModule's context, but it doesn't
import AuthenticationModule. In this case, it is not possible to get anything from
AuthenticationModule in the resolvers, because it is not imported. The following module doesn't
know anything about AuthenticationModule.
const SomeImportantModuleThatUsesAuthenticatedContext = new GraphQLModule({
typeDefs: SOME_TYPE_DEFS_HERE,
imports: [
// ...
// This module doesn't import AuthenticationModule
// ...
],
resolvers: {
// ...
Query: {
getUser(root, args, context) {
return context.user // Oops! Undefined!
}
}
// ...
}
})
To fix this, we need to import AuthenticationModule into that 'important' module to make it able
to access AuthenticationModule's context like below;
const SomeImportantModuleThatUsesAuthenticatedContext = new GraphQLModule({
typeDefs: SOME_TYPE_DEFS_HERE,
imports: [
// ...
// This module imports AuthenticationModule
AuthenticationModule
// ...
],
resolvers: {
// ...
Query: {
getUser(root, args, context) {
return context.user // Yes, we have that user HERE!
}
}
// ...
}
})
So, these examples above show us that the encapsulation can be very important in the long term of
our project development.
We think modular approach is not just merging schemas and concatenate context factory functions to
each other.
Having a tool that knows how to encapsulate modules and force this policy, makes it much
easier to write modular schema, and later, even reuse existing modules and share them across
multiple projects.
All Posts about GraphQL Modules
- GraphQL Modules — Feature based GraphQL Modules at scale
- Why is True Modular Encapsulation So Important in Large-Scale GraphQL Projects?
- Why did we implement our own Dependency Injection library for GraphQL-Modules?
- Scoped Providers in GraphQL-Modules Dependency Injection
- Writing a GraphQL TypeScript project w/ GraphQL-Modules and GraphQL-Code-Generator
- Authentication and Authorization in GraphQL (and how GraphQL-Modules can help)
- Authentication with AccountsJS & GraphQL Modules
- Manage Circular Imports Hell with GraphQL-Modules
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