Generator commands delegate Rails::Generator::Base and implement a standard set of actions. Their behavior is defined by the way they respond to these actions: Create brings life; Destroy brings death; List passively observes.

Commands are invoked by replaying (or rewinding) the generator‘s manifest of actions. See Rails::Generator::Manifest and Rails::Generator::Base#manifest method that generator subclasses are required to override.

Commands allows generators to "plug in" invocation behavior, which corresponds to the GoF Strategy pattern.

Methods
Public Instance methods
class_collisions(*class_names)

Does nothing for all commands except Create.

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    # File vendor/rails/railties/lib/rails_generator/commands.rb, line 52
52:         def class_collisions(*class_names)
53:         end
dependency(generator_name, args, runtime_options = {})

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    # File vendor/rails/railties/lib/rails_generator/commands.rb, line 45
45:         def dependency(generator_name, args, runtime_options = {})
46:           logger.dependency(generator_name) do
47:             self.class.new(instance(generator_name, args, full_options(runtime_options))).invoke!
48:           end
49:         end
invoke!()

Replay action manifest. RewindBase subclass rewinds manifest.

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    # File vendor/rails/railties/lib/rails_generator/commands.rb, line 41
41:         def invoke!
42:           manifest.replay(self)
43:         end
readme(*args)

Does nothing for all commands except Create.

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    # File vendor/rails/railties/lib/rails_generator/commands.rb, line 56
56:         def readme(*args)
57:         end
Protected Instance methods
current_migration_number()

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    # File vendor/rails/railties/lib/rails_generator/commands.rb, line 60
60:           def current_migration_number
61:             Dir.glob("#{RAILS_ROOT}/#{@migration_directory}/[0-9]*_*.rb").inject(0) do |max, file_path|
62:               n = File.basename(file_path).split('_', 2).first.to_i
63:               if n > max then n else max end
64:             end
65:           end
existing_migrations(file_name)

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    # File vendor/rails/railties/lib/rails_generator/commands.rb, line 75
75:           def existing_migrations(file_name)
76:             Dir.glob("#{@migration_directory}/[0-9]*_*.rb").grep(/[0-9]+_#{file_name}.rb$/)
77:           end
gsub_file(relative_destination, regexp, *args, &block)

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    # File vendor/rails/railties/lib/rails_generator/commands.rb, line 91
91:           def gsub_file(relative_destination, regexp, *args, &block)
92:             path = destination_path(relative_destination)
93:             content = File.read(path).gsub(regexp, *args, &block)
94:             File.open(path, 'wb') { |file| file.write(content) }
95:           end
migration_directory(relative_path)

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    # File vendor/rails/railties/lib/rails_generator/commands.rb, line 71
71:           def migration_directory(relative_path)
72:             directory(@migration_directory = relative_path)
73:           end
migration_exists?(file_name)

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    # File vendor/rails/railties/lib/rails_generator/commands.rb, line 79
79:           def migration_exists?(file_name)
80:             not existing_migrations(file_name).empty?
81:           end
next_migration_number()

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    # File vendor/rails/railties/lib/rails_generator/commands.rb, line 67
67:           def next_migration_number
68:             current_migration_number + 1
69:           end
next_migration_string(padding = 3)

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    # File vendor/rails/railties/lib/rails_generator/commands.rb, line 83
83:           def next_migration_string(padding = 3)
84:             if ActiveRecord::Base.timestamped_migrations
85:               Time.now.utc.strftime("%Y%m%d%H%M%S")
86:             else
87:               "%.#{padding}d" % next_migration_number
88:             end
89:           end