如何使用ActiveRecord匹配所有的“和”？

Question

我需要一个ActiveRecord查询来匹配params[]数组中的所有项。

我当前的方法是基于查找任何标签来给出结果，而不是“全部匹配”

class Product < ActiveRecord::Base
    has_many :tags

    def self.filter_by_params(params)
        scoped = self.scoped
        scoped = scoped.includes(:tags).where(:tags => {:id => params[:t]}) if params[:t]
        scoped
    end
end

我试着写一些类似下面的东西，但是它没有给我任何结果。有没有人能把我引向正确的方向？有没有一种方式可以说" AND "

def self.filter_by_params(params)
    scoped = self.scoped.includes(:tags)
    params[:t].each do |t|
        scoped = scoped.where(:tags => {:id => t})
    end
    scoped
end

Answer 1

如果我理解正确的话，params[:t]将是一个ID数组。如果是这种情况，你可以这样做：

def self.filter_by_params(params)
  scoped = self.scoped
  scoped = scoped.tags.find_all_by_id(params[:t])
  scoped
end

或者只是：

def self.filter_by_params(params)
  tags.find_all_by_id(params[:t])
end

Answer 2

您应该使用:joins而不是:includes

http://guides.rubyonrails.org/active_record_querying.html#specifying-conditions-on-the-joined-tables

class Product < ActiveRecord::Base
    has_many :tags

    def self.filter_by_params(params)
        scoped = self.scoped
        scoped = scoped.joins(:tags).where(:tags => {:id => params[:t]}) if params[:t]
        scoped
    end
end