rails - 已选择关联参数，但参数 "changing" 仍然存在

Question

我真的不知道如何描述这个问题，而且我以前从未遇到过这样的问题。我正在尝试建立一个 "has_many :through" 协会来处理对群组的成员资格请求。其他操作（销毁、更新）似乎工作正常。每当我在我的控制器中启动创建操作时，该对象都会显示它正在传递正确的参数并创建关联。但是，它只与 ID 为“1”的组建立关联。我不知道如何清楚地解释或解决这个问题。我会 post 我的日志和代码如下。

澄清我的问题：为什么数据 "changing" 持久化到数据库（创建时）？

Cliqs = 组

日志：

Started POST "/cliqs/2/cliq_requests" for ::1 at 2016-03-31 20:35:32 -0500
Processing by CliqRequestsController#create as HTML
Parameters: {"authenticity_token"=>"uaVHFgB7digMywl2a/n2GKMtwi691WA/dw2F2mzdkSCK69C46TZICiSp90xldj3hosFwSOPEi3fSOvOSkIVMjA==", "cliq_id"=>"2"}
Cliq Load (0.0ms)  SELECT  `cliqs`.* FROM `cliqs` WHERE (2) LIMIT 1
User Load (0.0ms)  SELECT  `users`.* FROM `users` WHERE `users`.`id` = 1  ORDER BY `users`.`id` ASC LIMIT 1
(0.0ms)  BEGIN
SQL (1.0ms)  INSERT INTO `cliq_requests` (`cliq_id`, `user_id`, `created_at`, `updated_at`) VALUES (1, 1, '2016-04-01 01:35:32', '2016-04-01 01:35:32')
(198.0ms)  COMMIT
Redirected to http://localhost:3000/cliqs
Completed 302 Found in 237ms (ActiveRecord: 199.0ms)

控制器操作：

def create
    @cliq = Cliq.find_by(params[:cliq_id])
    @cliq_request = current_user.cliq_requests.new(cliq: @cliq)

    if @cliq_request.save
        redirect_to cliqs_path
    else
        redirect_to current_user
    end 
end

其他操作（以防万一）：

def update
    @cliq = Cliq.find_by(params[:cliq_id])
    @cliq_request = CliqRequest.find(params[:id])
    @cliq_request.accept
end

def destroy
    @cliq = Cliq.find_by(params[:cliq_id])
    @cliq_request = CliqRequest.find(params[:id])
    @cliq_request.destroy
    if @cliq_request.destroy
        redirect_to cliqs_path
    else
        redirect_to current_user
    end
end

还有模特们：

class User < ActiveRecord::Base
has_one :owned_cliq, foreign_key: 'owner_id', class_name: 'Cliq', dependent: :destroy

has_many :cliq_memberships, dependent: :destroy
has_many :cliqs, through: :cliq_memberships

has_many :cliq_requests, dependent: :destroy

end

class Cliq < ActiveRecord::Base
belongs_to :owner, class_name: 'User'

has_many :cliq_memberships, dependent: :destroy
has_many :members, through: :cliq_memberships, source: :user

has_many :cliq_requests, dependent: :destroy                                
has_many :pending_members, through: :cliq_requests, source: :user, foreign_key: 'user_id'
end

class CliqRequest < ActiveRecord::Base
#from
belongs_to :user
#to
belongs_to :cliq

def accept
    cliq.members << cliq.pending_members.find(user_id)
    destroy
end
end

最后是我的观点：

<h1><%= @cliq.name %></h1>

<%= link_to 'Request to join Cliq', cliq_cliq_requests_path(@cliq, @cliq_request), :method => :post %>

<% @cliq_members.each do |cliq_member| %>
<ul><%= link_to cliq_member.username, user_path(cliq_member) %></ul>
<% end %>


<h3>Cliq Requests:</h3>

<ul>
<% @cliq.pending_members.each do |pending_member| %>
<%= link_to pending_member.username, user_path(pending_member) %>
<% end %>
<% @cliq.cliq_requests.each do |cliq_request| %>
<%= link_to "Accept", cliq_cliq_request_path(@cliq, cliq_request), :method => :put %>
<%= link_to "Deny", cliq_cliq_request_path(@cliq, cliq_request), :method => :delete %>
</ul>
<% end %>

Answer 1

正如您自己发现的那样，使用 @cliq = Cliq.find_by(id: params[:cliq_id]) 有效，而 @cliq = Cliq.find_by(params[:cliq_id]) 无效。那么为什么会这样呢？

find_by 方法根据条件进行匹配。使用 find_by，您可以匹配任何属性。例如，这也可以工作：

@cliq = Cliq.find_by(some_attribute: "foo")

因此使用 find_by，您必须指定 id 属性以便查询 return 正确的记录。您的 find_by 查询实际上是运行 SQL，看起来像这样：

SELECT  `cliqs`.* FROM `cliqs` WHERE (2) LIMIT 1

那个select语句会return整个table，而LIMIT 1只抓取第一条记录。

作为奖励，基于 params[:cliq_id] 分配 @cliq 的首选 rails 方法将仅使用 find，它使用其主要搜索记录键：

@cliq = Cliq.find(params[:cliq_id])

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