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Class: ActiveRecord::MigrationContext

Relationships & Source Files
Inherits: Object
Defined in: activerecord/lib/active_record/migration.rb

Overview

Migration Context

MigrationContext sets the context in which a migration is run.

A migration context requires the path to the migrations is set in the #migrations_paths parameter. Optionally a #schema_migration class can be provided. Multiple database applications will instantiate a SchemaMigration object per database. From the Rake tasks, Rails will handle this for you.

Class Method Summary

Instance Attribute Summary

Instance Method Summary

Constructor Details

.new(migrations_paths, schema_migration = nil, internal_metadata = nil) ⇒ MigrationContext

[ GitHub ] 

  


# File 'activerecord/lib/active_record/migration.rb', line 1205



def initialize(migrations_paths, schema_migration = nil, internal_metadata = nil)
  if schema_migration == SchemaMigration
    ActiveRecord.deprecator.warn(<<-MSG.squish)
      SchemaMigration no longer inherits from ActiveRecord::Base. If you want
      to use the default connection, remove this argument. If you want to use a
      specific connection, instantiate MigrationContext with the connection's schema
      migration, for example `MigrationContext.new(path, Dog.connection.schema_migration)`.
    MSG

    schema_migration = nil
  end

  if internal_metadata == InternalMetadata
    ActiveRecord.deprecator.warn(<<-MSG.squish)
      SchemaMigration no longer inherits from ActiveRecord::Base. If you want
      to use the default connection, remove this argument. If you want to use a
      specific connection, instantiate MigrationContext with the connection's internal
      metadata, for example `MigrationContext.new(path, nil, Dog.connection.internal_metadata)`.
    MSG

    internal_metadata = nil
  end

  @migrations_paths = migrations_paths
  @schema_migration = schema_migration || SchemaMigration.new(connection)
  @internal_metadata = internal_metadata || InternalMetadata.new(connection)
end


  







Instance Attribute Details



  

    #internal_metadata   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration.rb', line 1203



attr_reader :migrations_paths, :schema_migration, :internal_metadata


  








  

    #migrations_paths   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration.rb', line 1203



attr_reader :migrations_paths, :schema_migration, :internal_metadata


  








  

    #schema_migration   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration.rb', line 1203



attr_reader :migrations_paths, :schema_migration, :internal_metadata


  







Instance Method Details



  

    #migrate(target_version = nil, &block)  
  



  

    

Runs the migrations in the migrations_path.



If target_version is nil, migrate will run #up.



If the #current_version and target_version are both 0 then an empty array will be returned and no migrations will be run.



If the #current_version in the schema is greater than the target_version, then #down will be run.



If none of the conditions are met, #up will be run with the target_version.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration.rb', line 1246



def migrate(target_version = nil, &block)
  case
  when target_version.nil?
    up(target_version, &block)
  when current_version == 0 && target_version == 0
    []
  when current_version > target_version
    down(target_version, &block)
  else
    up(target_version, &block)
  end
end