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. For most applications, SchemaMigration is sufficient. Multiple database applications need a SchemaMigration per primary database.



[R] migrations_paths
[R] schema_migration

Class Public methods

new(migrations_paths, schema_migration = SchemaMigration)

# File activerecord/lib/active_record/migration.rb, line 1070
def initialize(migrations_paths, schema_migration = SchemaMigration)
  @migrations_paths = migrations_paths
  @schema_migration = schema_migration

Instance Public methods

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 less than the target_version, then down will be run.

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

# File activerecord/lib/active_record/migration.rb, line 1088
def migrate(target_version = nil, &block)
  when target_version.nil?
    up(target_version, &block)
  when current_version == 0 && target_version == 0
  when current_version > target_version
    down(target_version, &block)
    up(target_version, &block)