为什么我在Rails中搜索查询时出现“错误的参数数量（给定1，预期为0）”？

Question

此行引发错误“参数的错误数量（给定1，预期0）”。我真的很想知道如何让这个查询工作。谢谢！

@posts = Post.all(:joins => :course, :conditions => "course.name in (#{@user.courses.map(&:name).join(',')})",:order => "posts.created_at DESC") 

这是代码在我的控制器：

@user = current_user 
@posts = Post.all(:joins => :course, :conditions => "course.name in (#{@user.courses.map(&:name).join(',')})",:order => "posts.created_at DESC") 

下面是型号：

class Post < ActiveRecord::Base 
belongs_to :user 
belongs_to :course 
has_many :comments 
end 

class Course < ActiveRecord::Base 
belongs_to :user 
has_many :posts 
belongs_to :major 
end 

class User < ActiveRecord::Base 
# Include default devise modules. Others available are: 
# :confirmable, :lockable, :timeoutable and :omniauthable 
devise :database_authenticatable, :registerable, 
     :recoverable, :rememberable, :trackable, :validatable 

has_many :courses 
belongs_to :major 
has_many :posts 
has_many :comments 

accepts_nested_attributes_for :courses, reject_if: :all_blank,  allow_destroy: true 
end 

，这里是架构

create_table "comments", force: :cascade do |t| 
t.text  "comment" 
t.datetime "created_at", null: false 
t.datetime "updated_at", null: false 
t.integer "user_id" 
t.integer "post_id" 
end 

add_index "comments", ["post_id"], name: "index_comments_on_post_id" 
add_index "comments", ["user_id"], name: "index_comments_on_user_id" 

create_table "courses", force: :cascade do |t| 
t.string "name" 
t.datetime "created_at", null: false 
t.datetime "updated_at", null: false 
t.integer "major_id" 
t.integer "user_id" 
end 

add_index "courses", ["major_id"], name: "index_courses_on_major_id" 
add_index "courses", ["user_id"], name: "index_courses_on_user_id" 

create_table "majors", force: :cascade do |t| 
t.string "name" 
t.datetime "created_at", null: false 
t.datetime "updated_at", null: false 
end 

create_table "posts", force: :cascade do |t| 
t.string "title" 
t.text  "content" 
t.datetime "created_at", null: false 
t.datetime "updated_at", null: false 
t.integer "user_id" 
t.integer "course_id" 
end 

add_index "posts", ["course_id"], name: "index_posts_on_course_id" 
add_index "posts", ["user_id"], name: "index_posts_on_user_id" 

create_table "users", force: :cascade do |t| 
t.string "email",     default: "", null: false 
t.string "encrypted_password",  default: "", null: false 
t.string "reset_password_token" 
t.datetime "reset_password_sent_at" 
t.datetime "remember_created_at" 
t.integer "sign_in_count",   default: 0, null: false 
t.datetime "current_sign_in_at" 
t.datetime "last_sign_in_at" 
t.string "current_sign_in_ip" 
t.string "last_sign_in_ip" 
t.datetime "created_at",       null: false 
t.datetime "updated_at",       null: false 
t.boolean "admin" 
t.string "username" 
t.integer "major_id" 
end 

add_index "users", ["email"], name: "index_users_on_email", unique: true 
add_index "users", ["major_id"], name: "index_users_on_major_id" 
add_index "users", ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true 
add_index "users", ["username"], name: "index_users_on_username", unique: true 

end 

Answer 1

错误你得到在查询中是由于事实all方法不期望任何参数，它只是检索给定模型/关系的所有记录。

你想在这种情况下使用的是从ActiveRecord :: QueryMethods where方法。

还有一个错误是，您在条件中以单数形式使用表格的名称，它应该是复数（课程而不是课程）。

此外，您可以在这里使用includes方法结合references方法来生成数据库连接。

所以，你会像下面这样：

@posts = Post.includes(:course).where("courses.name IN (#{@user.courses.map(&:name).collect { |s| '#{s}' }.join(',') })").references(:courses).order("posts.created_at DESC")