I'm running into a number of cases in my current project where it
would be natural for a model's association data to be presented not as
an array but as an hash keyed by an attribute of the associated model,
typically a column from its composite primary key. For example:
class Player < Sequel::Model
one_to_many :game_data
end
class PlayerGameDatum < Sequel::Model
many_to_one :player
many_to_one :game
# PK might just be player_id, game_id, or might have additional
columns (e.g. datatype_id)
end
It's common to want to look up the data for a particular game given a
player. The default way to do this in sequel would be:
class Player < Sequel::Model
def data(game)
game_data.find_all{|datum| datum.game_id == game.id}
# or game_data_dataset.filter(:game_id => game.id).all
end
end
But that does either a linear search or a database query. I'd rather
be indexing into a hash. My solution thus far is:
def data(game)
@data ||= game_data.group_by {|datum| datum.game_id}
@data[game.id]
end
But now I'm storing the data in two different datastructures, and
really only using one of them. Plus I end up repeating similar code in
the Game class, to look up data by player.
Has anyone else dealt with this problem? What was your solution? Would
it make a good plugin or extension?
John
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