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STI Child Model Generator

The STI (Single Table Inheritance) child generator creates new Dream models that extend another Dream model, enabling you to leverage single table inheritance patterns. This generator creates complete models, just like the regular model generator, but with inheritance relationships.

Prerequisites: Creating the STI Parent​

Before generating STI children, you must first create the parent model, and it is recommended to use the --sti-base-serializer flag when doing so:

yarn psy g:resource --sti-base-serializer --owning-model=Place \
  v1/host/places/rooms Room type:enum:room_types:Bathroom,Bedroom,Kitchen,Den,LivingRoom \
  Place:belongs_to position:integer:optional deleted_at:datetime:optional

Why --sti-base-serializer? This flag creates the base serializer in a format that child serializers can properly extend, ensuring the inheritance hierarchy works correctly.

You can also create an STI parent using the model generator:

yarn psy g:model --sti-base-serializer \
  Room type:enum:room_types:Bathroom,Bedroom,Kitchen,Den,LivingRoom \
  Place:belongs_to position:integer:optional deleted_at:datetime:optional

Usage​

yarn psy g:sti-child <childModelName> extends <parentModelName> [columnsWithTypes...]

Arguments:

  • <childModelName>: The name of the child model to create (e.g., AdminUser or Premium/Account)
  • extends: The literal word "extends" (required)
  • <parentModelName>: Fully qualified name of the parent model (e.g., User or Health/Coach)
  • [columnsWithTypes...]: Additional properties specific to the child model

Options:

  • --no-serializer: Skip generating a serializer for the child model

STI Example​

This example creates an STI model for various rooms.

STI Base​

Create the base Room using the resource generator with the --sti-base-serializer flag:

yarn psy g:resource --sti-base-serializer --owning-model=Place \
  v1/host/places/rooms Room type:enum:room_types:Bathroom,Bedroom,Kitchen,Den,LivingRoom \
  Place:belongs_to position:integer:optional deleted_at:datetime:optional

Note that you’ll need to run yarn psy db:migrate after generating in order to run the next generator.

STI Child: Bathroom​

Then create an STI child:

yarn psy g:sti-child Room/Bathroom extends Room bath_or_shower_type:enum:bath_or_shower_types:bath,shower,bath_and_shower,none

Supported Column Types​

STI child models support the same column types as the model generator:

Basic Types​

  • citext: Case insensitive text
  • string: VARCHAR (default 255, customizable: name:string:128)
  • text: TEXT type for longer content
  • date: Date only
  • datetime: Timestamp with timezone
  • integer: Integer numbers

Advanced Types​

  • decimal: price:decimal:10,2 (10 total digits, 2 after decimal)
  • enum: status:enum:user_status:active,inactive,suspended
  • belongs_to: Role:belongs_to (creates foreign key and association)

Optional Columns​

Add :optional to make any column nullable:

yarn psy g:sti-child AdminUser extends User role:string:optional last_login:datetime:optional

How STI Works with Generators​

Single Table Inheritance allows multiple models to share the same database table while having different behaviors and attributes. The generators work together to create this setup:

Generator Workflow​

  1. Parent Model: Created with g:model or g:resource using --sti-base-serializer
  2. Child Models: Created with g:sti-child extending the parent

Database Structure​

  • Parent table: Contains columns for all child models
  • Type column: Automatically used to distinguish between child types (discriminator)
  • Shared columns: Common attributes inherited by all children
  • Child-specific columns: Additional columns added by child generators
Related Documentation