Ruby on Rails: Calling an instance method from another model

Question

I've got a Match model and a Team model. I want to run an instance method (written inside the Team model) after a Match has been saved. Here's what I've got.

team.rb

def goals_sum
  unless goal_count_cache
    goal_count = a_goals_sum + b_goals_sum
    update_attribute(:goal_count_cache, goal_count)
  end
  goal_count_cache
end

and it works. Now I need to run this whenever a match gets saved. So I tried this:

match.rb

after_save :Team.goals_sum
after_destroy :Team.goals_sum

And it doesn't work. I know I'm missing something basic, but I still can't go through with it. Any tips?

Does the match model has 2 relations to the teams playing the match? Like team_a and team_b? — mliebelt
– mliebelt, Commented Jan 11, 2013 at 12:47
@mliebelt - Yes, it has 2 relations: belongs_to :team_a, :class_name => 'Team', :foreign_key => 'team_a_id' (and the same for :team_b) — Kurt Bourbaki
– Kurt Bourbaki, Commented Jan 11, 2013 at 14:03

Andrew Haines · Accepted Answer · 2013-01-11 15:58:28Z

3

You can just define a private method on Match that delegates to the method on Team (otherwise, how would it know which team to run the method on? You say it's an instance method, and I assume a match has teams that are playing it).

after_save :update_teams_goals_sum
after_destroy :update_teams_goals_sum

private

def update_teams_goals_sum
  [team_a, team_b].each &:goals_sum
end

edited Jan 11, 2013 at 15:58

answered Jan 11, 2013 at 12:27

Andrew Haines

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1 Comment

Kurt Bourbaki Over a year ago

Thank you, that worked. I also had to correct a wrong part of the 'goals sum' definition in team.rb model, since it was using a wrong "unless" conditional that prevented the :goal_count_cache column in db to be updated.

Alex Lang · Accepted Answer · 2013-01-11 12:24:44Z

2

after_save :notify_team
after_destroy :notify_team

private

def notify_team
  Team.goals_sum
end

answered Jan 11, 2013 at 12:24

Alex Lang

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3 Comments

Andrew Marshall Over a year ago

That's not calling an instance method of Team.

Kurt Bourbaki Over a year ago

@Alex Lang - That would give me this error: undefined method `goals_sum' for #<Class:0xb6f61344>

Alex Lang Over a year ago

well, you still have to define def self.goals_sum on Team.

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