導軌的has_many找到相關項目

Question

於是，找來2款：

class Match < ActiveRecord::Base 
    has_many :rounds 
    has_many :participations 
    has_many :players, :through => :participations 
    belongs_to :clan_1, :class_name => "Clan", :foreign_key => "clan_1_id" 
    belongs_to :clan_2, :class_name => "Clan", :foreign_key => "clan_2_id" 
    belongs_to :winner, :class_name => "Clan", :foreign_key => "winner_id" 
    belongs_to :league 
    belongs_to :tournament 

    validates :clan_1_id, :presence => true 
    validates :clan_2_id, :presence => true 

    scope :by_league, lambda { |league| where("league_id == ?",league.id) } 
    scope :by_tournament, lambda { |tournament| where("tournament_id == ?",tournament.id) } 
    scope :played, where("played is not NULL") 
    scope :not_played, where("played is NULL") 


end 


class Clan < ActiveRecord::Base 
    has_many :players 
    has_many :rounds_won, :class_name => "Round", :foreign_key => "winner_id" 
    has_many :rounds_blue, :class_name => "Round", :foreign_key => "clan_blue_id" 
    has_many :rounds_purple, :class_name => "Round", :foreign_key => "clan_purple_id" 
    has_many :matches_won, :class_name => "Match", :foreign_key => "winner_id" 
    has_and_belongs_to_many :leagues 
    has_and_belongs_to_many :tournaments 


    def matches 
    Match.where("clan_1_id = ? OR clan_2_id = ?",self.id, self.id) 
    end 

    def matches_lost 
    matches.where("winner_id != ?", self.id) 
    end 

    def matches_drawn 
    matches.played.where("winner_id is NULL") 
    end 

end 

，我想獲取所有的氏族，這在比賽參加。

Answer 1

如果你改變你的團體，你可以利用一點點包括（）的範圍：

class Match < ActiveRecord::Base 
    belongs_to :clan_1, :class_name => "Clan" 
    belongs_to :clan_2, :class_name => "Clan" 
end 

class Clan < ActiveRecord::Base 
    has_many :one_matches, :class_name => 'Match', :foreign_key => :clan_1_id 
    has_many :two_matches, :class_name => 'Match', :foreign_key => :clan_2_id 
end 

然後你就可以添加此範圍：

class Clan < ActiveRecord::Base 
    scope :participated_in_match, includes(:one_matches, :two_matches).where("matches.id IS NOT NULL") 
end 

這不是測試所以請讓我知道，如果你得到意想不到的結果。

Answer 2

很簡單：

model_two_object = Model_2.first # For clarity only, change to suit your needs 
model_two_object.models_1 

Answer 3

你要仔細考慮。 Rails使你很容易做到這一點。

class Comment < ActiveRecord::Base 
    belongs_to :post 
end 

class Post < ActiveRecord::Base 
    has_many :comments 
end 

@post.comments 

如果您在您的評論表「MODELNAME」 _id（如POST_ID）軌與自動掛鉤外鍵的列。

您所要做的就是調用@ model1.model2，假定@ model1是model1對象的一個​​實例。

如果你想自己連接查詢，你可以使用where（）方法。

@comments = Comment.where(:post_id => some_id)