[GraphQL Centaur](https://github.com/graphql-editor/graphql-editor-cli) is a CLI tool with a goal to provide seamless experience creating GraphQL as a service.

GraphQL Centaur generates Mongo/[Stucco-js](https://github.com/graphql-editor/stucco-js) database resolvers in TypeScript from any give GraphQL Schema.

Generate fully-functional basic resolvers with Centaur CLI, customize them the way that suits your project and enjoy your GraphQL based backend.

## Installation

If you want to install GraphQL Centaur globally run:

```ts

npm i -g graphql-centaur
```

to install it inside your backend repo performer:

```ts

npm i graphql-centaur
```

then use with `npx` or as a `package.json` script.

| Database   | Support |
| ---------- | ------- |
| MongoDB    | YES     |
| JavaScript | YES     |
| TypeScript | YES     |
| PostgreSQL | SOON    |

## Resolver generation

First time when you generate a resolver centaur will also generate needed libraries for collections, DB, Utils and [graphql-zeus](https://github.com/graphql-editor/graphql-zeus) definitions, then given the following schema:

```ts
type Person{
    firstName: String!
}
type Query{
    people: [Person]!
}
schema{
    query: Query
}
```

after choosing the following elements:

* `Query`
* `people`
* `CRUD`
* `listFilter`

GraphQL Centaur should generate TypeScript resolver placed in `$src/Query/people.ts` directory:

```ts
import { FieldResolveInput, FieldResolveOutput } from 'stucco-js';
import { PersonCollection } from '../db/collections';
import { DB } from '../db/mongo';
import { Utils } from '../Utils';
import { Person, ResolverType, ValueTypes } from '../graphql-zeus';

export const handler = async (): Promise<FieldResolveOutput> => {
  const db = await DB();
  const col = await db.collection(PersonCollection);
  return Utils.CursorToGraphQLArray<Person>(await col.find({}));
};
```

and append correct entries to the [`stucco.json`](https://github.com/graphql-editor/stucco-js) file:

```ts
{
    "resolvers":{
        "Query.people":{
            "resolve":{
                "name":"lib/Query/people"
            }
        }
    }
}
```

After running [Stucco-js](https://github.com/graphql-editor/stucco-js), your resolver should work out of the box. Of course, some resolver types, however, might need a little bit of custom code to make them work the way you want, but basically **you have just generated your GraphQL Backend!**

## Available Resolvers

Resolvers are split into the following categories:

| Category   | Resolver           | Desc                                                                |
| ---------- | ------------------ | ------------------------------------------------------------------- |
| **CRUD**   | *Create*           | Create an object in your database and return it                     |
| **CRUD**   | *Update*           | Update an object in your database and return it                     |
| **CRUD**   | *List*             | List all objects of selected type                                   |
| **CRUD**   | *Get* by parameter | Get object by parameter from the database                           |
| **CRUD**   | *Remove*           | Remove an object from the database and return true                  |
| **COMMON** | *Pipe*             | Pipe the arguments of the query as the source for the next resolver |
| **COMMON** | *Resolver*         | Simple Resolver you need to write                                   |
| **COMMON** | *Rest*             | Rest proxy resolvers for pointing to existing REST APIs             |
| **COMMON** | *Source*           | A Resolver that receives source from the parent resolver            |
| **COMMON** | *SourcedCRUD*      | The same as CRUD, but also use source                               |

GraphQL Centaur is also compatible with [GraphQL Editor projects](https://graphqleditor.com/).

Generate GraphQL resolvers easily with GraphQL Centaur

Ready for take-off?

Unlocking the Power of React 19

Welcome to a short post about a recent quality of life update to GraphQL Zeus. If you're not familiar with GraphQL Zeus go ahead and read my [earlier post which breaks down its basics](/what-is-graphql-zeus). If you are lets go ahead and talk about the update!

### Graphql Fragments

GraphQL has long supported reusable fields natively with the use of fragments. If you're not familiar with them basically if you had the same fields in multiple queries you could define a fragment - a set of fields, and then reuse it instead of repeating all the fields every time. Lets say you had a user with some fields like name, email, address. Then you could use a fragment like this:

```ts
query getUser {
  user(id: 4) {
    ...userFields
  }
}

fragment userFields on User {
  name,
  email,
  address,
  avatar
}
```

For reusability you could put all your fragments in a fragments.js file and then use them across a project. Zeus already had a solution like Selectors (which work a bit similarly to that) but with the latest update it can now go a step further! :)

### Zeus fields - GraphQL spread operator

For our example lets say we need to get the posts data for our blog page where we display them in a grid, usually the query that would look something like this:

```ts
const posts = await Chain('http://example.com/api/graphql')('query')({
  posts: [
    {
      title: true,
      coverImage: true,
      publishedAt: true,
      slug: true,
      content: { markdown: true },
    },
  ],
});
```

With Zeus 6.0.0 you can simply use a spread operator `...fields` with the TypeScript type from the schema (eg. `Post`) to simply get all the fields available for that type:

```ts
const posts = await Chain('http://example.com/api/graphql')('query')({
  posts: [
    {
      ...fields('Post'),
    },
  ],
});
```

### Never go full REST

With this, we now have a convenient quality-of-life improvement for cases where you just want to quickly retrieve all the fields for a type. That said it's important to remember what GraphQL is all about - getting exactly what you requested without overfetching. So don't just use `...fields` everywhere or you'll defeat the entire purpose of using GraphQL in the first place and turn it into REST, always pulling way more data than necessary.


Zeus update - GraphQL spread operator

GraphQL Zeus is codegen which, with the use of just one command, generates Typescript types for your GraphQL schema. From there even a junior frontend dev can easily handle writing type-safe requests to the backend, and do so without asking backend devs or even looking at the schema. To showcase how easy it is lets go over the installation and some basic use cases.

### Installation and example query

1. Obviously first we need to install it in our project using `npm i graphql-zeus`.
2. Once it finishes installing we need to point it to our schema url using the command `zeus http://example.com/your-schema-url/`. Zeus will then generate types for everything in that schema and put that in a file in its folder so that you can easily import it across your project.

### Queries

Now we can begin writing type safe requests. Lets say our example will be a simple query which fetches reviews which we then put into a table, list, carousel or whatever else on our website:

```ts
const reviews = await Chain('http://example.com/your-schema-url/')('query')({
  listReviews: [
    {
      author_name: true,
      rating: true,
      content: true,
    },
  ],
});
```

That will give us all the reviews as an array, we can then easily map over it to create some simple component like this:

```ts
{
  reviews.map((review, idx) => {
    return (
      <div key={idx} className="flex flex-col">
        <h3>{review.author_name}</h3>
        <div>{'★'.repeat(review.rating)}</div>
        <p>{review.content}</p>
      </div>
    );
  });
}
```

Queries follow a simple structure: we use square brackets for their contents and then:

- in the first curly brackets we put the query payload ie. what we're sending to the backend (for example the id of the item we want to get, the locale or the access token for a login query)
- in the second curly brackets we specify which fields we want to receive

Following our example lets say we're interested in getting our reviews in only one language - then we would have to specify that in the query payload(autocomplete is your friend here and will tell you exactly what you can input there):

```ts
const reviews = await Chain('http://example.com/your-schema-url/')('query')({
  listReview: [
    { locale: 'pl' },
    {
      author_name: true,
      rating: true,
      content: true,
    },
  ],
});
```

### Mutations

With mutations instead of retrieving data, we're sending it to the backend to make changes. The structure is the same as with queries, two sets of curly brackets:

- in the first brackets one we include the inputs ie. what we want to change (like add a new review or modify an existing one by id)
- in the second brackets we specify what we want to get back after the mutation runs, which is usually a confirmation that the mutation was successful

Sticking with our previous example we can create a mutation to submit reviews:

```ts
const newReview = await Chain('http://example.com/your-schema-url/')(
  'mutation',
)({
  createReview: [
    { input: { author_name: 'John', rating: 5, content: 'Great product!' } },
    {
      id: true,
    },
  ],
});
```

This will only create a 5 star review by John with that content. Most likely you'd want to link that to some small form component which lets users write reviews and sends that mutation with the data on submit or something similar.

### Use with CMS (Hygraph)

If we're reusing queries or mutations across our project it makes little sense to keep writing them out like that. It makes more sense to put them in a specific file and then import them as needed. For this example lets say we're pulling data from a CMS like Hygraph, we can create a file called `requests.ts`. Then at the top of it we can create a custom Chain which will handle the url and authorization (we'll be using it for all our queries and mutations since Hygraph wont let us through otherwise):

```ts
export const chain = Chain(process.env.CMS_URL!, {
  headers: {
    Authorization: `Bearer ${process.env.CMS_TOKEN}`,
  },
});
```

Now we can create a query to get all our blogposts from the CMS and even limit those to only the ones in English and only those in the Published stage o that we avoid getting drafts and such:

```ts
export const getPosts = async () => {
  return await chain('query')({
    posts: [
      {
        stage: Stage.PUBLISHED,
        locales: [Locale.en],
      },
      {
        title: true,
        author: true,
        coverImage: true,
        publishedAt: true,
        slug: true,
        content: { markdown: true },
      },
    ],
  });
};
```

From here using it in our component is a simple as doing a const and then putting the data in a map, list, carousel or whatever we want.

```ts
const blogposts = await getPosts();
{
  blogposts.map((blogpost, idx) => {
    return <BlogCard key={idx} />;
  });
}
```

GraphQL's core concept is getting only what you request without overfetching so if we want to get just one blogpost we'll need a specific query for that. Lets say we want to make dynamic pages for our blogposts using slugs, for that we'll need to pass that to the CMS in the payload and then we'll receive only the post we asked for. We also need to throw an error in case an incorrect slug was provided or something else went wrong, so lets use a simple try catch:

```ts
const getPostBySlug = async ({ slug }: { slug: string }) => {
  try {
    const result = await Chain('query')({
      post: [
        {
          stage: Stage.PUBLISHED,
          locales: [Locale.en],
          where: { slug: slug },
        },
        {
          title: true,
          author: true,
          coverImage: true,
          publishedAt: true,
          slug: true,
          content: { markdown: true },
        },
      ],
    });
    return result;
  } catch (error) {
    console.error('Could not get post, error:', error);
    throw error;
  }
};
```

### Zeus Selectors

Writing out all the fields we want returned every single time would be cumbersome, and that's where Selectors come in. Since Zeus generates types for the entire schema it makes writing Selectors much easier with the use of autocomplete and type-safety. As we were querying for blogposts it makes the most sense to go with a Post Selector as an example:

```ts
export const postSelector = Selector('Post')({
  title: true,
  author: true,
  coverImage: true,
  publishedAt: true,
  slug: true,
  content: { markdown: true },
});
```

Thanks to that instead of writing out all the fields we can just use a selector like this:

```ts
export const getPosts = async () => {
  return await chain('query')({
    posts: [
      {
        stage: Stage.PUBLISHED,
        locales: [Locale.en],
      },
      postSelector,
    ],
  });
};
```

And that's all for the basic use cases, hopefully this guide was simple enough to follow and now you're ready to use Zeus for your projects and find out yourself how handy it is for working with the backend. I can say it definitely worked wonders for me as a very junior frontend dev. If you have any questions or want to know more, feel free to reach out and stay tuned for the next post, where I’ll dive into a recent update to Zeus and how it can make things even easier!


Category	Resolver	Desc
CRUD	Create	Create an object in your database and return it
CRUD	Update	Update an object in your database and return it
CRUD	List	List all objects of selected type
CRUD	Get by parameter	Get object by parameter from the database
CRUD	Remove	Remove an object from the database and return true
COMMON	Pipe	Pipe the arguments of the query as the source for the next resolver
COMMON	Resolver	Simple Resolver you need to write
COMMON	Rest	Rest proxy resolvers for pointing to existing REST APIs
COMMON	Source	A Resolver that receives source from the parent resolver
COMMON	SourcedCRUD	The same as CRUD, but also use source

Generate GraphQL resolvers easily with GraphQL Centaur

Installation

Resolver generation

Available Resolvers

Check out our other blogposts

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