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.
Methods
Attributes
| [R] | internal_metadata | |
| [R] | migrations_paths | |
| [R] | schema_migration |
Class Public methods
new(migrations_paths, schema_migration = nil, internal_metadata = nil)
📝 Source code
# File activerecord/lib/active_record/migration.rb, line 1217
def initialize(migrations_paths, schema_migration = nil, internal_metadata = nil)
@migrations_paths = migrations_paths
@schema_migration = schema_migration || SchemaMigration.new(connection_pool)
@internal_metadata = internal_metadata || InternalMetadata.new(connection_pool)
endInstance 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 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.
📝 Source code
# File activerecord/lib/active_record/migration.rb, line 1236
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