[英]Getting value from associated model
我的設置:Rails 2.3.10,Ruby 1.8.7
這是我的模特
class User
has_many :user_projects
end
class Project
has_many :user_projects
#has a column named "project_type"
end
class UserProject
belongs_to :user
belongs_to :project
#fields: project_id, user_id
end
當我返回用戶及其相關的user_projects記錄的JSON字符串時,我還想在user_project記錄中包括project.project_type列。 注意:我不想在結果中也包含整個項目記錄。 一個可能的解決方案是在user_projects中的project_type字段中復制,但是如果可能的話,我不願意這樣做,是否有另一種方法可以在查找/讀取操作期間完成此操作?
為了清楚起見,這是我正在尋找的JSON輸出
{
"user": {
"username": "bob",
"id": 1,
"email": "bob@blah.com"
"user_projects": [
{
"id": 15,
"user_id": 1,
"project_id": 10,
"project_type": "marketing"
}
{
"id": 22,
"user_id": 1,
"project_id": 11,
"project_type": "sales"
}
]
}
您可以嘗試在嵌套的include中使用:only
鍵:
user.to_json(:include => {:user_projects => {:include => {:project => {:only => :type}}}})
但是我將has_many :projects, :through => :user_projects
到User中,這樣您可以做得更簡單:
user.to_json(:include => {:projects => {:only => [:id, :type]}})
另外,還有一個離題的警告提示:除非使用STI,否則不要在Rails中使用“類型”作為列名(即,項目類型是Project的ruby子類)。
-
編輯
這是一種將project_type
添加到UserProject的方法
class UserProject
belongs_to :user
belongs_to :project
delegate :type, :to => :project, :prefix => true
end
user.to_json(:include => {:user_projects => {:methods => :project_type}})
class UserProject
belongs_to :user
belongs_to :project
#fields: project_id, user_id
attr_reader :type
def type
self.project.type
end
end
class MyController < AC
def action
@model = whatever
respond_to do |format|
format.json { render :json => @model.to_json(:methods => :type)}
end
end
end
希望這可以幫助。
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