ruby-on-rails - コレクションを使用するときに中間オブジェクトを取得するにはどうすればよいですか<

Question

After having defined a has_many :through relationship,

@user = User.New(:name=>"Bob")
@project = Project.New( :name=>"Market Survey")
@user.projects << @project

Is there an easy way to fetch the new intermediate object it creates? such as in the above example, if the intermediate table is `memberships' then I could use:

@membership = @user.projects << @project

I have this feeling that there must be a better way of doing this than what we do all the time, i.e

@membership = Membership.where(:user_id=>x , :project_id=>y).first

score 3 · Accepted Answer

There's no 'magic' way of doing this that I'm aware of. If you're looking for something that reads better than what you've done so far, the best I can come up with is to do something like this:

class User < ActiveRecord::Base
  # ... other active record stuff here.

  def membership_for(project)
    memberships.where(:project_id => project.id).first
  end
end

# Somewhere else...
@user = User.new(:name=>"Bob")
@project = Project.new(:name=>"Market Survey")
@user.projects << @project
@user.save!

membership = @user.membership_for(@project)

Not perfect, and requires additional code, but it does read better than your current code, and that counts for a lot in Ruby.

score 0 · Accepted Answer

I'm not sure if I understand your question, If one user has many projects, i think you can use this:

@user = User.create(:name=>"Bob")

# Create project and membership with user_id of @user same time, return project.
@project = @user.projects.create(:name=>"Market Survey")

If you want to find a membership, i think there is another way:

@membership = Membership.find(:first, conditions: { user_id: x, project_id: y })

score 0 · Accepted Answer

次のようなことができます：

@membership = @user.members.find_by_project_id(@project.id)

あなたがしていることよりも簡単/良いかどうかはわかりません。

3 に答える 3

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