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Holds common methods for migrations. It assumes that migrations have the [0-9]*_name format and can be used by other frameworks (like Sequel) just by implementing the next migration version method.

Methods
C
M
S

Attributes

[R] migration_class_name
[R] migration_file_name
[R] migration_number

Instance Public methods

create_migration(destination, data, config = {}, &block)

Source: show | on GitHub 

# File rails/railties/lib/rails/generators/migration.rb, line 35
def create_migration(destination, data, config = {}, &block)
  action Rails::Generators::Actions::CreateMigration.new(self, destination, block || data.to_s, config)
end

migration_template(source, destination, config = {})

Creates a migration template at the given destination. The difference to the default template method is that the migration version is appended to the destination file name.

The migration version, migration file name, migration class name are available as instance variables in the template to be rendered.

migration_template "migration.rb", "db/migrate/add_foo_to_bar.rb"

Source: show | on GitHub 

# File rails/railties/lib/rails/generators/migration.rb, line 56
def migration_template(source, destination, config = {})
  source = File.expand_path(find_in_source_paths(source.to_s))

  set_migration_assigns!(destination)
  context = instance_eval("binding")

  dir, base = File.split(destination)
  numbered_destination = File.join(dir, ["%migration_number%", base].join("_"))

  file = create_migration numbered_destination, nil, config do
    if ERB.instance_method(:initialize).parameters.assoc(:key) # Ruby 2.6+
      ERB.new(::File.binread(source), trim_mode: "-", eoutvar: "@output_buffer").result(context)
    else
      ERB.new(::File.binread(source), nil, "-", "@output_buffer").result(context)
    end
  end
  Rails::Generators.add_generated_file(file)
end

set_migration_assigns!(destination)

Source: show | on GitHub 

# File rails/railties/lib/rails/generators/migration.rb, line 39
def set_migration_assigns!(destination)
  destination = File.expand_path(destination, destination_root)

  migration_dir = File.dirname(destination)
  @migration_number     = self.class.next_migration_number(migration_dir)
  @migration_file_name  = File.basename(destination, ".rb")
  @migration_class_name = @migration_file_name.camelize
end