Page Contents

Prerequisites

Important: Before running this generator, make sure the models, datasource, and repositories involved in this relation exist. Then, inside your LoopBack 4 application, run the command from the root directory.

Synopsis

Adds a new Relation between existing source and target models in a LoopBack application.

lb4 relation [options]

Options

  • -h, --help: Print the generator’s options and usage.
  • --skip-cache: Do not remember prompt answers. Default: false.
  • --skip-install: Do not automatically install dependencies. Default: false.
  • --force-install: Fail on install dependencies error. Default: false.
  • --relationType: Relation type.
  • --sourceModel: Source model.
  • --destinationModel: Destination model.
  • --throughModel: Through model. For HasManyThrough relation only.
  • --sourceModelPrimaryKey: The name of the primary key of the source model.
  • --sourceModelPrimaryKeyType: The type of the primary key of the source model.
  • --destinationModelPrimaryKey: The name of the primary key of the destination model.
  • --destinationModelPrimaryKeyType: The type of the primary key of the destination model.
  • --foreignKeyName: Destination/Source model foreign key name for HasMany,HasOne/BelongsTo relation, respectively.
  • --relationName: Relation name.
  • --sourceKeyOnThrough: Foreign key that references the source model on the through model. For HasManyThrough relation only.
  • --targetKeyOnThrough: Foreign key that references the target model on the through model. For HasManyThrough relation only.
  • -c, --config: JSON file name or value to configure options.
  • -y, --yes: Skip all confirmation prompts with default or provided value.
  • --format: Format generated code using npm run lint:fix.

Arguments

Defining lb4 relation in one command line interface (cli):

lb4 relation --sourceModel=<sourceModel>
--destinationModel=<destinationModel> --foreignKeyName=<foreignKeyName>
--relationType=<hasMany|hasOne|belongsTo> [--relationName=<relationName>]
[--sourceModelPrimaryKey=<sourceModelPrimaryKey>]
[--sourceModelPrimaryKeyType=<sourceModelPrimaryKeyType>]
[--destinationModelPrimaryKey=<destinationModelPrimaryKey>]
[--destinationModelPrimaryKeyType=<destinationModelPrimaryKeyType>]
[--format]

  • <relationType> - Type of the relation that will be created between the source and target models.

  • <sourceModel> - Name of the model to create the relationship from.

  • <destinationModel> - Name of the model to create a relationship with.

  • <sourceModelPrimaryKey> - Name of the id property on the model to create the relationship from.

  • <sourceModelPrimaryKeyType> - Type of the id property on the source model.

  • <destinationModelPrimaryKey> - Name of the id property on the model to create a relationship with.

  • <destinationModelPrimaryKeyType> - Type of the id property on the destination model.

  • <foreignKeyName> - Property that references the primary key property of the destination model.

  • <relationName> - Name of the relation that will be created.

After setting up the definition for the relation, you need to confirm if you want to register the inclusion resolver for this relation:

? Allow <sourceModel> queries to include data from related <destinationModel> instances? (Y/n)

Check the site Relations and the Querying Related Models section in each relation for more use cases.

HasManyThrough

Defining a HasManyThrough relation via the CLI is a bit different from defining HasMany, HasOne, or BelongsTo relations.

lb4 relation --sourceModel=<sourceModel>
--destinationModel=<destinationModel> --throughModel=<throughModel>
--relationType=<hasManyThrough> [--relationName=<relationName>]
[--sourceModelPrimaryKey=<sourceModelPrimaryKey>]
[--sourceModelPrimaryKeyType=<sourceModelPrimaryKeyType>]
[--destinationModelPrimaryKey=<destinationModelPrimaryKey>]
[--destinationModelPrimaryKeyType=<destinationModelPrimaryKeyType>]
[--sourceKeyOnThrough=<sourceKeyOnThrough>] [--targetKeyOnThrough<targetKeyOnThrough>]
[--format]

  • <throughModel> - Name of the model to reference the source model and target model.

  • <sourceKeyOnThrough> - Property on the through model that references the primary key property of the source model.

  • <targetKeyOnThrough> - Property on the through model that references the primary key property of the target model.

Interactive Prompts

The tool will prompt you for:

  • Relation type between models (relationBaseClass). Prompts a list of available relations to choose from as the type of the relation between the source model and the target model. Supported relation types:

  • Name of the source model (sourceModel). Prompts a list of available models to choose from as the source model of the relation.

  • Name of the target model (targetModel). Prompts a list of available models to choose from as the target model of the relation.

  • Name of the through model (targetModel). Prompts a list of available models to choose from as the through model of the relation. For HasManyThrough relation only.

  • Name of the foreign key (foreignKeyName). Prompts a property name that references the primary key property of the another model. Note: Leave blank to use the default. For HasMany/BelongsTo/HasOne relations.

    Default values: <sourceModel> + Id in camelCase, e.g categoryId

  • Name of the source key (sourceKeyOnThrough). Prompts a property name that references the source model to define on the through model. For HasManyThrough relation only. Default value: <sourceModel> + Id in camelCase, e.g doctorId.

  • Name of the target key (targetKeyOnThrough). Prompts a property name that references the target model to define on the through model. For HasManyThrough relation only. Default value: <targetModel> + Id in camelCase, e.g patientId.

  • Name of the relation (relationName). Prompts for the Source property name. Note: Leave blank to use the default. Default values:

    • plural form of <targetModel> for hasMany and hasManyThrough relations, e.g. products
    • singular form of <targetModel> for hasOne relations, e.g. address
    • for belongsTo relations, the default name is based on the foreign key of the belongsTo relation. E.g. when the foreign key is the default name, categoryId for example, the default relation name is category.

It might also prompt for names and types of the source/destination models if they cannot be detected from model files.

The generator has some limitations. It only asks the most basic factors for generating relations. For example, it uses the id property as the source key. LB4 allows you customize the source key name, the foreign key name, the relation name, and even the DB column name. Check the Relation Metadata section in each relation to learn how you can define relations.

Output

Once all the prompts have been answered, the CLI will update or create source files for the Entities involved in the relation.

  • Update source Model class as follows: /src/models/${sourceModel-Name}.model.ts
  • Update target Model class as follows: /src/models/${targetModel-Name}.model.ts
  • Update source Model Repository class as follows: /src/repositories/${sourceModel-Repository-Name}.repository.ts
  • Update target Model Repository class as follows: /src/repositories/${targetModel-Repository-Name}.repository.ts
  • Create a Controller for the new relation as follows: /src/controllers/{sourceModel-Name}-{targetModel-Name}.controller.ts
  • Update /src/controllers/index.ts to export the newly created Controller class.