HABTM关系查找所有记录，但不包括基于关联的记录 [英] HABTM relation find all records, excluding some based on association

问题描述

我看过与此相关的一些类似SO帖子，但我一直在努力解决这个问题。

I've looked at some of the similar SO posts relating to this but I'm struggling to get my head around it.

我之间存在着一种害羞的关系项目和用户。我正在尝试查找特定用户不属于的所有项目，但我不知道怎么做。

I have a habtm relation between Projects and Users. I'm trying to find all the Projects that a particular user does not belong to but I don't know how.

我已经尝试过这种事情：

I've tried this sort of thing:

Project.where('project_id != ?', user.id)

但这显然也是错误的。

我正在使用rails 3.2.x

I'm using rails 3.2.x

与该提及的示波器有关的许多答案，但我以前从未见过（我对Rails还是很陌生）。

Many of the answers relating to this mention scopes but I haven't come across them before (I'm still very new to Rails).

我刚发现这使用一个答案提示发布： Project.where（'id not in（？）'，user.projects）

I just found this post with one answer suggesting: Project.where('id not in (?)', user.projects)

这似乎可行，除了 user.projects 为空时。我正在尝试 Project.where（'id not in（？）'，（d.projects.empty？？''，d.projects））
正如JosephCastro的答案注释线程中所建议的那样，但是它在第二个 d.projects 中给了我一个语法错误。

which seems to work, except when user.projects is empty. I'm trying Project.where('id not in (?)', (d.projects.empty? ? '', d.projects)) as is suggested in JosephCastro's answer comment thread but it's giving me a syntax error on the second d.projects.

编辑

与用户相关的项目模型摘要

Project model snippet that relates to Users

class Project < ActiveRecord::Base
  attr_accessible ...
  has_and_belongs_to_many :users, :before_add => :validates_unique

，然后

class User < ActiveRecord::Base
  attr_accessible ...
  has_and_belongs_to_many :projects

推荐答案

您可以像这样在您的项目模型中放置一个范围：

You can place a scope in your Project model like so:

scope :not_belonging_to, lambda {|user| joins(:projects_users).where('projects_users.user_id <> ?', user.id) }}

这假定您的联接表名称与 HABTM 关联的rails约定

This assumes your join table name matches rails convention for HABTM associations

要获得的项目用户不属于用户，请首先找到您的用户，然后将其传递给范围，例如：

To then get projects that a user doesn't belong to, first find your user, then pass them to the scope like so:

@user = User.find(params[:id]) # example
@unowned_projects = Project.not_belonging_to(@user)

反思时，该范围将不起作用，因为它将发现拥有多个开发人员的项目，如果其中一个是您的人。

On reflection, that scope won't work as it will find projects that have more than one developer, if one of those is your guy.

相反，请使用以下内容：

Instead, use the following:

scope :not_belonging_to, lambda {|user| where('id NOT IN (?)', user.projects.empty? ? '' : user.projects) }

这篇关于HABTM关系查找所有记录，但不包括基于关联的记录的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！