objection-graphql

Automatic GraphQL API generator for objection.js models.

Usage

objection-graphql automatically generates a GraphQL schema for objection.js models. The schema is created based on the jsonSchema and relationMappings properties of the models. It creates a rich set of filter arguments for the relations and provides a simple way to add custom filters.

The following example creates a schema for three models Person, Movie and Review and executes a GraphQL query:

const graphql = require('graphql').graphql;
const graphQlBuilder = require('objection-graphql').builder;

// Objection.js models.
const Movie = require('./models/Movie');
const Person = require('./models/Person');
const Review = require('./models/Review');

// This is all you need to do to generate the schema.
const graphQlSchema = graphQlBuilder()
  .model(Movie)
  .model(Person)
  .model(Review)
  .build();

// Execute a GraphQL query.
graphql(graphQlSchema, `{
  movies(nameLike: "%erminato%", range: [0, 2], orderBy: releaseDate) {
    name,
    releaseDate,
    
    actors(gender: Male, ageLte: 100, orderBy: firstName) {
      id
      firstName,
      age
    }
    
    reviews(starsIn: [3, 4, 5], orderByDesc: stars) {
      title,
      text,
      stars,
      
      reviewer {
        firstName
      }
    }
  }
}`).then(result => {
  console.log(result.data.movies);
});

The example query used some of the many default filter arguments. For example the nameLike: "%erminato%" filter is mapped into a where clause where name like '%erminato%'. Similarily the ageLte: 100 is mapped into a where age <= 100 clause. In addition to the property filters there are some special arguments like orderBy and range. Check out this table for a full list of filter arguments available by default.

Getting started

If you are already using objection.js the example in the usage section is all you need to get started. If you are unfamiliar with objection.js you should try our example project.

Filters

argument	type	action
`prop: value`	property type	`prop = value`
`propEq: value`	property type	`prop = value`
`propGt: value`	property type	`prop > value`
`propGte: value`	property type	`prop >= value`
`propLt: value`	property type	`prop < value`
`propLte: value`	property type	`prop <= value`
`propLike: value`	string	`prop LIKE value`
`propIsNull: value`	boolean	`prop IS NULL` or `prop IS NOT NULL`
`propIn: value`	Array	`prop IN value`
`propNotIn: value`	Array	`prop NOT IN value`
`propLikeNoCase: value`	string	`lower(prop) LIKE lower(value)`

Special arguments

argument	action
`orderBy: prop`	Order the result by some property
`orderByDesc: prop`	Order the result by some property in descending order
`range: [start, end]`	Select a range. Doesn't work for relations!

Adding your own custom arguments

Here's an example how you could implement a NotEq filter for primitive values:

const graphql = require('graphql');

const graphQlSchema = graphQlBuilder()
  .model(Movie)
  .model(Person)
  .model(Review)
  .argFactory((fields, modelClass) => {
    const args = {};

    _.forOwn(fields, (field, propName) => {
      // Skip all non primitive fields.
      if (field.type instanceof graphql.GraphQLObjectType 
          || field.type instanceof graphql.GraphQLList) {
        return;
      }
    
      args[propName + 'NotEq'] = {
        // For our filter the type of the value needs to be 
        // the same as the type of the field.
        type: field.type,
        
        query: (query, value) => {
          // query is an objection.js QueryBuilder instance.
          query.where(propName, '<>', value);
        }
      };
    });

    return args;
  })
  .build();

Misc

defaultArgNames

You can change the default filter suffixes and special filter names using the defaultArgNames method:

const graphQlSchema = graphQlBuilder()
  .model(Movie)
  .model(Person)
  .model(Review)
  .defaultArgNames({
    eq: '_eq',
    gt: '_gt',
    gte: '_gte',
    lt: '_lt',
    lte: '_lte',
    like: '_like',
    isNull: '_is_null',
    likeNoCase: '_like_no_case',
    in: '_in',
    notIn: '_not_in',
    orderBy: 'order_by',
    orderByDesc: 'order_by_desc',
    range: 'range'
  })
  .build();

Now you would have myProp_lt: value instead of the default myPropLt: value.

By default the model names are pluralized by adding an s to the end of the camelized table name. You can set a custom plural and singular names for the root fields like so:

const graphQlSchema = graphQlBuilder()
  .model(Movie)
  .model(Person, {
    listFieldName: 'people',
    fieldName: 'person'
  })
  .model(Review)

onQuery

You can modify the root query by passing an object with onQuery method as the third argument for graphql method:

const graphQlSchema = graphQlBuilder()
  .model(Movie)
  .model(Person)
  .model(Review)
  .build();

expressApp.get('/graphql', (req, res, next) => {
  graphql(graphQlSchema, req.query.graph, {
    // builder is an objection.js query builder.
    onQuery(builder) {
      // You can for example store the the logged in user to builder context
      // so that it can be accessed from model hooks.
      builder.mergeContext({
        user: req.user
      });
      
      // Or change the eager fetching algorithm.
      builder.eagerAlgorithm(Model.JoinEagerAlgorithm);
    }
  }).then(result => {
    res.send(result);
  }).catch(err => {
    next(err);
  });
});

maxwellsmart84 / objection-graphql