【rspec】FactoryBotのbelongs_to、has_many実装方法

class Project < ApplicationRecord
	has_many :users
end

class User < ApplicationRecord
	belongs_to :project
end

FactoryBot.define do
	factory :user do
		association :project
	end
end

FactoryBot.define do
	factory :project
end

FactoryBot.create(:user) # UserとProjectを作成して保存

FactoryBot.build(:user) # UserとProjectを作成（保存されない）

user = FactoryBot.build(:user)
user.save # UserとProjectの両方が保存される

# 基本形
association :project

# association :project の省略形。factory名と関連名が同じ場合にこう書ける。
project

# factoryを指定することも可能。
association :project, factory: :sub_project

# Projectの属性を上書きできる。
association :project, project_name: 'プロジェクトA'

my_project = Project.create(name: '私のプロジェクト')
FactoryBot.create(:user, project: my_project)

project_id { Project.create(name: 'my project').id }

project_id { 1 }

# ID指定に抵抗がある場合は、定数にしておくと良いかも
project_id { ProjectData::MY_PROJECT_ID }

class User < ApplicationRecord
	belongs_to :project, optional: true
end

FactoryBot.define do
	factory :user do

		factory :user_with_project do
			association :project
		end
	end
end

FactoryBot.create(:user) # Projectは作成されない
FactoryBot.create(:user_with_project) # Projectも作成される

FactoryBot.define do
	factory :user

	trait :with_project do
		association :project
	end
end

FactoryBot.create(:user) # Projectは作成されない
FactoryBot.create(:user, :with_project) # Projectも作成される

FactoryBot.define do
	factory :project, traits: [:with_users] do

		trait :with_users do
			transient do
				users_count { 0 }
			end

			after(:build) do |project, evaluator|
				evaluator.users_count.each do
					project.users << FactoryBot.build(:user, project: project)
				end
			end
		end
	end
end

FactoryBot.create(:project) # Userが一緒に作成されない
FactoryBot.create(:project, users_count: 5) # Userが５件作成される

class Project < ApplicationRecord
	has_many :categories, through: project_categories
	has_many :project_categories
end

class ProjectCategory < ApplicationRecord
	belongs_to :project
	belongs_to :category
end

class Category < ApplicationRecord
end

FactoryBot.define do
	factory :project, traits: [:with_categories] do

		trait :with_categories do
			transient do
				my_categories { [] }
			end

			after(:build) do |project, evaluator|
				evaluator.my_categories.each do |category_id|
					project.categories << FactoryBot.build(:project_category, category_id: category_id,  project_id: project.id)
				end
			end
		end
	end
end

FactoryBot.create(:project) # Categoryに所属なし
FactoryBot.create(:project, my_categories: [1, 2]) # Categoryにふたつ所属