def initialize( position, name, opts = {}, &block )
@position, @name = position, name
@options = opts
@database = DataMapper.repository(@options[:database] || :default)
@adapter = @database.adapter
case @adapter.class.to_s
when /Sqlite3/ then @adapter.extend(SQL::Sqlite3)
when /Mysql/ then @adapter.extend(SQL::Mysql)
when /Postgres/ then @adapter.extend(SQL::Postgresql)
else
raise "Unsupported Migration Adapter #{@adapter.class}"
end
@verbose = @options.has_key?(:verbose) ? @options[:verbose] : true
@up_action = lambda {}
@down_action = lambda {}
instance_eval &block
end