[Rails] Re: Math between Models
Okay great, thanks! I think I'll actually trying doing this in the join table. I guess my last question would be how would I call that method from that join table in let's say the Player show view? -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com. To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
[Rails] Re: Math between Models
Sa S. wrote in post #1074690: > Thanks for the help! Although I'm not sure I totally understand it, > still a bit of a noob. So if I wanted to do something as simple as > subtract the user's handicap from the course's handicap, how would I > create a method for that in the Player model? (sorry maybe you might > have done it already but I'm not sure what .gt and .lt mean) Forgot to mention ".gt" and ".lt" means "greater than" and "less than" respectively. -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com. To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
[Rails] Re: Math between Models
Sa S. wrote in post #1074690: > Thanks for the help! Although I'm not sure I totally understand it, > still a bit of a noob. So if I wanted to do something as simple as > subtract the user's handicap from the course's handicap, how would I > create a method for that in the Player model? (sorry maybe you might > have done it already but I'm not sure what .gt and .lt mean) > > Basically something like > > class Player > > def handicaps_difference >Course.handicap - handicap (from the player) > end Given that with a many-to-many relationship (has_and_belongs_to_many) a single player will be associated to many courses and one course will be associated to many players. So in order to do that sort of math you'll need to iterate through them. Player will have a method, added by ActiveRecord named "courses"... a_player.courses I assume here that you want to first select a player: a_player = Player.find(:id) Then I assume you want to list all the courses associated with this one player with the handicap difference: a_player.courses.each do |course| puts course.handicap_difference(a_player) end Where each course can calculate the handicap difference with a given player: class Course def handicap_different(player) player.handicap - self.handicap end end But even better would be to expose the join table with its own object using has_many :through. Then you can put the calculation in the object that "knows" about both sides: class CourseAssignment # The exposed join table has_one :player has_one :course def handicap_difference player.handicap - course.handicap end end Again the "player" and "course" methods will be added by ActiveRecord to the CourseAssignment object. http://guides.rubyonrails.org/association_basics.html#choosing-between-has_many-through-and-has_and_belongs_to_many -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com. To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
[Rails] Re: Math between Models
Thanks for the help! Although I'm not sure I totally understand it, still a bit of a noob. So if I wanted to do something as simple as subtract the user's handicap from the course's handicap, how would I create a method for that in the Player model? (sorry maybe you might have done it already but I'm not sure what .gt and .lt mean) Basically something like class Player def handicaps_difference Course.handicap - handicap (from the player) end -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com. To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
[Rails] Re: Math between Models
Robert Walker wrote in post #1074687: > class Player > def recommended_courses > Course.where(courses[:handicap].gt(a_player.handicap)) > .and(courses[:handicap].lt(a_player.handicap) > end > end Just realized after posting that this is a silly example, but should get you on the right track. Should have been something like courses[:handicap].gt(a_player.handicap - 5).and(courses[:handicap].lt(a_player.handicap + 5)) Sorry I don't know anything about golf, so that may still sound ridiculous from the perspective of a golf handicap. I hope it at least helps with the programming issue. -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com. To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
[Rails] Re: Math between Models
Sa S. wrote in post #1074685: > Hi Michael, > > Thanks for the reply. > > I actually have created the join table as documented in the rails > guides, with the right naming convention and all. It's got a model_1_id > and a model_2_id, and an index > > Sure, I can give some more details. I'm creating a golf application that > let's users enter in some information about their golf game, and then > shows them appropriate golf courses. > > So I've got one model called 'Course' that is just a bunch of seed data. > Then I've got another model called 'Player' that contains all the > user-entered information via a form. > > Ultimately, I have a Player 'show' view that shows a table with the > appropriate golf courses, along with some other information. One of > these other pieces of information is a mathematical function that > compares the user's entered handicap with the course's. > > So all of my methods are in the Player model, and for this handicap > function, I'm trying to pull in the Course's handicap attribute to do > the math. Rails provides methods for accessing associations between models. You should not need to use foreign keys directly as shown in your original post. Given: 1. Player has many courses 2. Course has many players Example: a_player = Player.first players_courses = a_player.courses player_courses.each do |course| puts course.handicap end class Player def recommended_courses Course.where(courses[:handicap].gt(a_player.handicap)) .and(courses[:handicap].lt(a_player.handicap) end end These examples are for demonstration only. They are completely untested or checked for syntax. -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com. To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
[Rails] Re: Math between Models
Hi Michael, Thanks for the reply. I actually have created the join table as documented in the rails guides, with the right naming convention and all. It's got a model_1_id and a model_2_id, and an index Sure, I can give some more details. I'm creating a golf application that let's users enter in some information about their golf game, and then shows them appropriate golf courses. So I've got one model called 'Course' that is just a bunch of seed data. Then I've got another model called 'Player' that contains all the user-entered information via a form. Ultimately, I have a Player 'show' view that shows a table with the appropriate golf courses, along with some other information. One of these other pieces of information is a mathematical function that compares the user's entered handicap with the course's. So all of my methods are in the Player model, and for this handicap function, I'm trying to pull in the Course's handicap attribute to do the math. Hope that makes sense -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com. To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
