CODEWITHSUNDEEP
ruby-on-railsrubyactiverecordmany-to-many
Saggex
Saggex

Reputation: 3500

How to access data through many_to_many relation?

How do I Access data through this Many_to_Many relation?

Here are my database creations:

The "Useres":

class CreateSubgroups < ActiveRecord::Migration
  def change
    create_table :subgroups do |t|
      t.string :name
      t.belongs_to :group

      t.timestamps
    end
  end
end

The relationship:

class CreateRtimespans < ActiveRecord::Migration
  def change
        create_table :rtimespans do |t|
            t.belongs_to :subgroup_id
            t.belongs_to :timespan_id
        end
    end 
end

The Used:

class CreateTimespans < ActiveRecord::Migration
  def change
    create_table    :timespans do |t|
      t.string      :name
      t.text        :descrition
      t.integer     :start_h
      t.integer     :start_m
      t.integer     :end_h
      t.integer     :end_m
    end
  end
end

How do I for example access the names of all timespans, that belong to one subgroup? And vis versa, how can I show, which subgroups use a specific timespan?

Upvotes: 0

Views: 75

Answers (2)

Ashish Chopra
Ashish Chopra

Reputation: 1439

As your code suggest you have got two models as

Subgroup

and

TImespan

since there is a many to many relation between them we can use them as

# all timespans related to a subgroup
subgroup.timespans # where variable subgroup is a Subgroup object

and

# all subgroups related to a timespan
timespan.subgroups # where variable timespan is a Timespan object

Upvotes: 1

Andreas Lyngstad
Andreas Lyngstad

Reputation: 4927

First question

You can do whatever find call as long as you get a instance. I get a instance by calling .first on the model.

Subgroup.first.timespans.each do |timespan|
   puts timespan.name
end

Vis versa

Timespan.first.subgroups.each do |subgroup|
   puts subgroup.name
end

Upvotes: 1

Related Questions