typeorm-relations

A toolkit for working with TypeORM relations objects.

Installation

npm i typeorm-relations

This library is written in TypeScript, so type definitions are included in the box.

You must also install typeorm v0.3.x as a peer dependency (you should have this already).

Introduction

Relations in TypeORM are used to describe related objects. When defining your schema you can declare properties on your entities as representing either one-to-one, many-to-one, one-to-many, or many-to-many relations to other entities.

When fetching an entity, you use the relations option on Repository/EntityManager findX() methods to tell TypeORM which of the entity's related entities should also be fetched from the database at the same time, by way of SQL JOIN clauses.

TypeORM v0.3.0 introduced a new object format for the relations option. In earlier versions it only accepted an array of strings, but the new object format allows for better type safety. A FindOptionsRelations object looks like this:

{
    profile: true,
    photos: true,
    videos: {
        videoAttributes: true,
    },
}

It's easy enough to write out relations objects by hand. But what if you need to select relations conditionally, or generate your relations based on some other information? Then you may find you want an easy way to manipulate relations objects by adding or removing entries, or merging multiple relations objects together.

That's where typeorm-relations comes in! It's a toolkit for working with relations objects.

Usage

Use the RelationMap class to work with relations when you're performing a query.

A simple example:

import { RelationMap } from 'typeorm-relations';

const userRelationMap = new RelationMap<User>({
  profile: true,
  photos: true,
  videos: {
    videoComments: true,
  },
});

if (needsVideoAttributes) {
  userRelationMap.add({
    videos: {
      videoAttributes: true,
    },
  });
}

const users = await userRepository.find({
  /*
   * When needsVideoAttributes === true, this will be equivalent to:
   *
   * relations: {
   *   profile: true,
   *   photos: true,
   *   videos: {
   *     videoComments: true,
   *     videoAttributes: true,
   *   },
   * }
   */
  relations: userRelationMap.toFindOptionsRelations(),
});

RelationMap

RelationMap.constructor(initial?: FindOptionsRelations | RelationMap)

Instantiate with new RelationMap(). Pass a relations object to the constructor to set the initial value.

new RelationMap<User>({ profile: true });

RelationMap.add(relationsToAdd: FindOptionsRelations | RelationMap | string | string[]): this

Mutates the RelationMap instance by adding relations. It's smart about merging relation objects, so that a true value for a relation property will not clobber an existing object value containing nested relations.

Accepts several kinds of input:

1. Add a relations object, or another RelationMap instance, to merge the values.

   Example:

   const relationMapA = new RelationMap<User>({
     profile: true,
     videos: true,
   });
   const relationMapB = new RelationMap<User>({
     photos: {
       photoAttributes: true,
     },
     videos: true,
   });
   
   relationMapA.add({
     videos: {
       videoAttributes: true,
     },
   });
   relationMapA.add(relationMapB);

   Results in relationMapA containing the value:

   {
     profile: true,
     videos: {
       videoAttributes: true
     },
     photos: {
       photoAttributes: true
     }
   }
   

2. Add a single relation property by key name. Note: this only works with properties that exist at the top level of the given entity.

   const relationMap = new RelationMap<User>({
     profile: true,
     videos: true,
   });
   relationMap.add('photos');

   Results in relationMap containing the value:

   {
     profile: true,
     videos: true,
     photos: true
   }
   

3. Add a single relation property by key path, specified as an array of strings.

   const relationMap = new RelationMap<User>({
     profile: true,
     videos: true,
   });
   relationMap.add(['photos', 'photoAttributes']);

   Results in relationMap containing the value:

   {
     profile: true,
     videos: true,
     photos: {
       photoAttributes: true
     }
   }
   

RelationMap.remove(relationsToRemove: FindOptionsRelations | RelationMap | string | string[]): this

Mutates the RelationMap instance by subtracting relations. Removing a nested path will remove all relations below the given level.

Accepts input in the form of a relations object, another RelationMap instance, or a single relation given by key name or key path array.

Example:

const relations = new RelationMap<User>({
  profile: true,
  photos: {
    photoAttributes: true,
  },
  videos: {
    videoAttributes: true,
  },
});

relations.remove({
  videos: {
    videoAttributes: true,
  },
});

Results in relations containing the value:

{
  profile: true,
  photos: {
    photoAttributes: true
  },
  videos: true,
}

RelationMap.toFindOptionsRelations(): FindOptionsRelations

Returns a plain object representation of the relations, suitable for use with any of TypeORM's repository methods that accept find options.

Example:

const products = await dataSource.getRepository(Product).find({
  relations: relationMap.toFindOptionsRelations(),
  where: { ... },
  order: { ... }
})

If you are using a SelectQueryBuilder, you can join the relations using setFindOptions() like this:

queryBuilder.setFindOptions({ relations: relationMap.toFindOptionsRelations() });

RelationMap.has(path: string | string[]): boolean

Accepts a relation path as a string or an array of strings and returns a boolean indicating whether the relation at that path is selected for retrieval in the RelationMap. If a single string is given as the path, it should refer to a top level key of the entity, whereas an array path may look into deeper levels of relations.

Example:

const relationMap = new RelationMap<User>({
  photos: {
    photoAttributes: true,
  },
  videos: true,
});

if (relationMap.has('photos') && relationMap.has('videos')) {
  console.log('User.photos and User.videos will be selected!');
}

if (relationMap.has(['photos', 'photoAttributes'])) {
  console.log('User.photos.photoAttributes will be selected!');
}

Utility functions

If you prefer a more functional style, you can use these utilities directly instead of using the RelationMap class.

mergeRelations(relationsA: FindOptionsRelations, relationsB: FindOptionsRelations): FindOptionsRelations

Returns a new relations object containing the result of merging the two relations objects passed as arguments.

Example:

import { mergeRelations } from 'typeorm-relations';

mergeRelations<User>({ profile: true }, { photos: { photoAttributes: true } });

Returns the value:

{
  profile: true,
  photos: {
    photoAttributes: true
  }
}

subtractRelations(relations: FindOptionsRelations, relationsToSubtract: FindOptionsRelations): FindOptionsRelations

Returns a new relations object containing the result of subtracting the second relation object from the first.

Example:

import { subtractRelations } from 'typeorm-relations';

subtractRelations<User>(
  {
    profile: true,
    photos: { photoAttributes: true },
  },
  {
    photos: { photoAttributes: true },
  },
);

Returns the value:

{
  profile: true,
  photos: true
}

addRelationByPath(relations: FindOptionsRelations, path: string[]): FindOptionsRelations

Returns a new relations object containing the result of adding a relation property by key path, specified as an array of strings.

Example:

import { addRelationByPath } from 'typeorm-relations';

addRelationByPath<User>({ profile: true }, ['photos', 'photoAttributes']);

Returns the value:

{
  profile: true,
  photos: {
    photoAttributes: true
  }
}

removeRelationByPath(relations: FindOptionsRelations, path: string[]): FindOptionsRelations

Returns a new relations object containing the result of removing a relation property by key path, specified as an array of strings.

Example:

import { removeRelationByPath } from 'typeorm-relations';

removeRelationByPath<User>({ profile: true, photos: { photoAttributes: true } }, ['photos', 'photoAttributes']);

Returns the value:

{
  profile: true,
  photos: true
}

License

MIT