Persistence with rom-rb

Exercises

Setup

• bundle install

Getting started, writing data

• Write a migration for an "articles" table
  • id primary key, title text, and published boolean columns
• Create a relation (with inferred schema)
• Create a repo for the relation
• Create some records
  • enable create command on repo
• Use #by_pk to read records back
• Update some records
  • enable update comand on repo using by_pk restriction

Building queries

• Add methods to repository to query and return multiple records
  • listing of published articles
• Move lower-level query methods into relation
  • #published method in relation
  • update repository to use this method
  • create some articles where published is both true and false, ensure they're returned as appropriate
• Add methods to repository to return single records
• Create shared articles method in repository to ensure all query methods return only published articles
• Return results as custom structs via a custom struct namespace

Reading aggregates

• Write a migration for an associated "authors" table
  • id primary key and name text column
  • add author_id foreign key to "articles" table
• Add a relation for the table and declare associations
  • declare belongs_to :author association in "articles" relation
• Create a repository for authors, with "create" command enabled
• Create author records
• Create article records with author_id attribute filled
• In "articles" repository, return aggregate objects including the articles' authors

Changesets

• Implement publish(author, article) in the articles repository that will use :create changeset to create a new article, mark it as published and associate with the author
• Implement unpublish(article) in the articles repository that will use :update changeset to mark the article as not published

Further exploration...

Building queries

• Return custom structs using map_to
• Investigate using dry-struct to build custom struct classes with strict attribute types

Testing

• Write tests for your repository methods
  • Use rom-factory to create records
  • Write tests to assert that repository methods return appropriate records