[英]Getting value from associated model
我的设置:Rails 2.3.10,Ruby 1.8.7
这是我的模特
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
当我返回用户及其相关的user_projects记录的JSON字符串时,我还想在user_project记录中包括project.project_type列。 注意:我不想在结果中也包含整个项目记录。 一个可能的解决方案是在user_projects中的project_type字段中复制,但是如果可能的话,我不愿意这样做,是否有另一种方法可以在查找/读取操作期间完成此操作?
为了清楚起见,这是我正在寻找的JSON输出
{
"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"
}
]
}
您可以尝试在嵌套的include中使用:only
键:
user.to_json(:include => {:user_projects => {:include => {:project => {:only => :type}}}})
但是我将has_many :projects, :through => :user_projects
到User中,这样您可以做得更简单:
user.to_json(:include => {:projects => {:only => [:id, :type]}})
另外,还有一个离题的警告提示:除非使用STI,否则不要在Rails中使用“类型”作为列名(即,项目类型是Project的ruby子类)。
-
编辑
这是一种将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
希望这可以帮助。
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