Question

我有很多材料的项目，我正在尝试制作一系列范围来过滤它们：

与论文相关联的

project1 。与塑料

相关联的 project2

如果用户点击纸张，我希望显示 project1 和 project2 。如果在第一次查询之后用户点击塑料，我想用新约束过滤第一个查询结果。

换句话说，如果我选择纸张和塑料，我只想显示 project2 。

我的模特：

项目模型

class Project < ApplicationRecord
    has_many :project_materials
    has_many :materials, through: :project_materials

    scope :with_materials, -> (materials) { includes(:materials).where(materials: {id: materials} ) }
end

材料模型：

class Material < ApplicationRecord
  has_many :project_materials
  has_many :projects, through: :project_materials
end

project_material模型：

class ProjectMaterial < ApplicationRecord
  belongs_to :project
  belongs_to :material
end

我在rails控制台中尝试了以下内容：

p1 = Project.first
p2 = Project.last
m1 = Material.first
m2 = Material.last

p1.materials << m1

p2.materials << m1
p2.materials << m2

f1 = Project.with_materials(m1)
# which return p1 and p2

f2 = f1.with_materials(m2)
# which return nothings because of the following query

'SQL (1.0ms)  SELECT "projects"."id" AS t0_r0, "projects"."name" AS t0_r1, "projects"."difficulty" AS t0_r2, "projects"."status" AS t0_r3, "projects"."duration" AS t0_r4, "projects"."uuid" AS t0_r5, "projects"."slug" AS t0_r6, "projects"."created_at" AS t0_r7, "projects"."updated_at" AS t0_r8, "projects"."project_type_id" AS t0_r9, "materials"."id" AS t1_r0, "materials"."name" AS t1_r1, "materials"."created_at" AS t1_r2, "materials"."updated_at" AS t1_r3 FROM "projects" LEFT OUTER JOIN "project_materials" ON "project_materials"."project_id" = "projects"."id" LEFT OUTER JOIN "materials" ON "materials"."id" = "project_materials"."material_id" WHERE "materials"."id" = 5'

提前谢谢。

Answer 1

我有一个解决方案可能不是最优雅的，但至少它正在发挥作用。

def self.with_materials materials
  materials = [materials].flatten.compact

  sql = "SELECT project_id, count(material_id) FROM project_materials WHERE material_id IN (?) GROUP BY project_id HAVING count(material_id) > ?"
  ids = ProjectMaterial.find_by_sql [sql, (materials), (materials.count - 1)]
  ids.collect!{ |i| i.project_id }

  where( id: ids )
end

ActiveRecord has_many通过链式过滤器

1 个答案: