DeclareSchema

Declare your Rails/active_record model schemas and have database migrations generated for you!

Example

Make a model and declare your schema within a fields do ... end block:

class Company < ActiveRecord::Base
  fields do
    company_name :string, limit: 100
    ticker_symbol :string, limit: 4, null: true, index: true, unique: true
    employee_count :integer
    comments :text

    timestamps
  end

  belongs_to :industry
end

Then generate the migration:

$ rails generate declare_schema:migration

---------- Up Migration ----------
create_table :companies, id: :bigint do |t|
  t.string   :company_name, null: false, limit: 100
  t.string   :ticker_symbol, limit: 4
  t.integer  :employee_count, null: false
  t.text     :comments, null: false
  t.datetime :created_at
  t.datetime :updated_at
  t.integer  :industry_id, null: false
end
add_index :companies, [:ticker_symbol], unique: true, name: 'on_ticker_symbol'
add_index :companies, [:industry_id], name: 'on_industry_id'
execute "ALTER TABLE companies ADD CONSTRAINT index_companies_on_industry_id FOREIGN KEY index_companies_on_industry_id(industry_id) REFERENCES industries(id) "
----------------------------------

---------- Down Migration --------
drop_table :companies
----------------------------------


What now: [g]enerate migration, generate and [m]igrate now or [c]ancel?  g
  => "g"

Migration filename: [<enter>=declare_schema_migration_1|<custom_name>]: add_company_model

Note that the migration generator is interactive -- it can't tell the difference between renaming something vs. adding one thing and removing another, so sometimes it will ask you to clarify.

Migrator Configuration

The following configuration options are available for the gem and can be used during the initialization of your Rails application.

before_generating_migration callback

During the initializtion process for generating migrations, DeclareSchema will trigger the eager_load! on the Rails application and all Rails::Engines loaded into scope. If you need to generate migrations for models that aren't automatically loaded by eager_load!, load them in the before_generating_migration block.

Example Configuration

DeclareSchema::Migration::Migrator.before_generating_migration do
  require 'lib/some/hidden/models.rb'
end

Declaring Character Set and Collation

Note: This feature currently only works for MySQL database configurations.

MySQL originally supported UTF-8 in the range of 1-3 bytes (mb3 or "multi-byte 3") which covered the full set of Unicode code points at the time: U+0000 - U+FFFF. But later, Unicode was extended beyond U+FFFF to make room for emojis, and with that UTF-8 require 1-4 bytes (mb4 or "multi-byte 4"). With this addition, there has come a need to dynamically define the character set and collation for individual tables and columns in the database. With declare_schema this can be configured at three separate levels

Global Configuration

The character set and collation for all tables and fields can be set at the global level using the Generators::DeclareSchema::Migrator.default_charset= and Generators::DeclareSchema::Migrator.default_collation= configuration methods.

For example, adding the following to your config/initializers directory will turn all tables into utf8mb4 supporting tables:

declare_schema.rb

# frozen_string_literal: true

Generators::DeclareSchema::Migration::Migrator.default_charset   = "utf8mb4"
Generators::DeclareSchema::Migration::Migrator.default_collation = "utf8mb4_general"

Table Configuration

In order to configure a table's default character set and collation, the charset and collation arguments can be added to the fields block.

For example, if you have a comments model that needs utf8mb4 support, it would look like the following:

app/models/comment.rb

# frozen_string_literal: true

class Comment < ActiveRecord::Base
  fields charset: "utf8mb4", collation: "utf8mb4_general" do
    subject :string, limit: 255
    content :text,   limit: 0xffff_ffff
  end
end

Field Configuration

If you're looking to only change the character set and collation for a single field in the table, simply set the charset and collation configuration options on the field definition itself.

For example, if you only want to support utf8mb4 for the content of a comment, it would look like the following:

app/models/comment.rb

# frozen_string_literal: true

class Comment < ActiveRecord::Base
  fields do
    subject :string, limit: 255
    context :text,   limit: 0xffff_ffff, charset: "utf8mb4", collation: "utf8mb4_general"
  end
end

Installing

Install the DeclareSchema gem directly:

  $ gem install declare_schema

or add it to your bundler Gemfile:

  gem 'declare_schema'

Testing

To run tests:

rake test:prepare_testapp[force]
rake test:all < test_responses.txt