Company has many users とします。
class Company < ApplicationRecord
has_many :users
end
class User < ApplicationRecord
belongs_to :company
end
会社をひとつつくる
Company.create(name: 'kinop')
=> #<Company:0x00000005e599d0
id: 1,
name: "kinop",
created_at: Mon, 19 Jun 2017 05:44:02 UTC +00:00,
updated_at: Mon, 19 Jun 2017 05:44:02 UTC +00:00>
Company.count => 1
ユーザを3人つくる
1.upto(3) do |i|
User.create(name: "name#{i}", company_id: 1)
end
User.count => 3
問題1
company = Company.first
company.users.count # => ?
問題2
company = Company.first
company.users.size # => ?
問題3
company = Company.first
company.users.length # => ?
問題4
company = Company.first
company.users.length # => 3
User.create(name: "name4", company_id:1)
puts "#{company.users.length} #{company.users.size} #{company.users.count}"
解答
問題1 => 3
問題2 => 3
問題3 => 3
問題4 => 3 3 4