has_many至少有兩個條目

Question

我需要一個至少有兩個條目的has_many關聯，我如何編寫驗證以及如何使用RSpec + factory-girl測試它？這是我到現在爲止，但它與ActiveRecord::RecordInvalid: Validation failed: Bars can't be blank失敗，我完全卡在RSpec測試。

/example_app/app/models/foo.rb

class Foo < ActiveRecord::Base 
    has_many :bars 
    validates :bars, :presence => true, :length => { :minimum => 2} 
end 

/example_app/app/models/bar.rb

class Bar < ActiveRecord::Base 
    belongs_to :foo 
    validates :bar, :presence => true 
end 

/示例應用內/規格/工廠/ foo.rb

FactoryGirl.define do 
    factory :foo do 
    after(:create) do |foo| 
     FactoryGirl.create_list(:bar, 2, foo: foo) 
    end 
    end 
end 

/example-app/spec/factories/bar.rb

FactoryGirl.define do 
    factory :bar do 
    foo 
    end 
end 

Answer 1

class Foo < ActiveRecord::Base 
    validate :must_have_two_bars 

    private 
    def must_have_two_bars 
    # if you allow bars to be destroyed through the association you may need to do extra validation here of the count 
    errors.add(:bars, :too_short, :count => 2) if bars.size < 2 
    end 
end 


it "should validate the presence of bars" do 
    FactoryGirl.build(:foo, :bars => []).should have_at_least(1).error_on(:bars) 
end 

it "should validate that there are at least two bars" do 
    foo = FactoryGirl.build(:foo) 
    foo.bars.push FactoryGirl.build(:bar, :foo => nil) 
    foo.should have_at_least(1).error_on(:bar) 
end 

Answer 2

你想用一個自定義的驗證

class Foo < ActiveRecord::Base 
    has_many :bars 
    validate :validates_number_of_bars 

    private 
    def validates_number_of_bars 
    if bars.size < 2 
     errors[:base] << "Need at least 2 bars" 
    end 
    end 
end