set_primary_key error in Rails

问题

I'm creating a table called Index. Here's the migration:

class CreateIndices < ActiveRecord::Migration
  def change
    create_table :indices, {:id => false} do |t|
      t.string :name
      t.float :returns, array: true, default: []
      t.float :navs, array: true, default: []
      t.float :sharpe

      t.timestamps
    end

    execute "ALTER TABLE indices ADD PRIMARY KEY (name);"
  end
end

That all works fine. I saw in another Stack Overflow question that I have to include the set_primary_key command in my model to get it to work, so I have the following in the index.rb

class Index < ActiveRecord::Base
  set_primary_key :name

end

Besides these two files, I haven't changed anything from the default Rails scaffolding (the app was created with Postgres as the default database). When I go to localhost:3000/indices, I get the following error

undefined method `set_primary_key' for #<Class:0x37132e0>

If I comment out the set_primary_key line it loads the regular empty scaffold, but I assume this does not give me the primary key functionality that I want. What am I doing wrong?

回答1:

If you're using rails 3.2 or higher, the set_primary_key method was depreciated, check out the Rails 3.2 release notes - Section 8.1 and it suggests using an assignment method instead like self.primary_key=, just like you said you did in your comment

回答2:

Exactly it's currently a class method :

http://api.rubyonrails.org/classes/ActiveRecord/AttributeMethods/PrimaryKey/ClassMethods.html#method-i-primary_key-3D

Don't forget the adequate migration :

def up

    create_table :books, {id: false, primary_key: :key_id} do |t|
      t.timestamps
      etc.
    end

    execute <<-SQL
        ALTER TABLE books
        ADD PRIMARY KEY (key_id)
    SQL

end

def down

    drop_table :books

end

If you want to use this new primary key in your generated routes (routes.rb) :

resources :books, only: [:show, :edit, :update], param: :key_id

Hope it helps !

Take care

回答3:

Weird. As per documentation I would have expected

class Index < ActiveRecord::Base
    set_primary_key "name"
end

to work. The only difference I can see is "name" string vs your :name symbol which shouldn't make any difference.

Update

Actually, bang up the top of that link is a deprecated message (sorry). Apparently it's now a class method so that explains the need for self.set_primary_key. Doh!

来源：https://stackoverflow.com/questions/20386636/set-primary-key-error-in-rails

标签

ruby-on-rails

primary-key