Rails:belongs_to多个>方法 [英] Rails: belongs_to multiple > Methods

问题描述

我刚刚完成了Michael Hartl Rails教程.试图做我自己的东西.

I just finished the Michael Hartl Rails Tutorial. Trying to make something of my own.

我很难理解自己想要建立的关系.我将尽力简化此过程.一棵有树枝，树枝和树叶的树是合适的，但是...

I am having trouble with getting rails to understand the relationships I'm trying to create. I'll try to simplify this as much as possible. A tree with branches, twigs and leaves would be apt, but...

我将以父子格式为例.因此，我自然有用户，可以说用户创建了家庭.

I'll use the parent child format as an example. So naturally I have users, and let's say users create families.

所以:

Class User < ActiveRecord::Base

 has_many :families
 has_many :parents
 has_many :children

end

Class Family < ActiveRecord::Base

 belongs_to :user
 has_many :parents

end

Class Parent < ActiveRecord::Base

 belongs_to: :user
 belongs_to: :family
 has_many: :children

end

Class Child < ActiveRecord::Base

 belongs_to :user
 belongs_to :parent

end

如您所见，我希望孩子属于属于家庭的父母，但是孩子本身不属于家庭，除非通过父母.如果这不是一个隐喻，那是可悲的，但在这种特殊情况下是正确的. ;)

As you can see, I want a child to belong to the parent which belongs to the family, but the child itself does not belong to a family except through the parent. Sad if this weren't a metaphor, but true in this particular case. ;)

我已经在父母"下尝试过

I have tried under Parent:

has_many :children, through: :parent

和

has_many :children, through: :family

但这没用.

当我尝试使用时:

User.family.new

或

User.child.new 

...它说该方法不存在.我的意思是说它不了解这些关系.

...it says the method doesn't exist. I take that to mean that it isn't understanding the relationships.

我在做什么错了?

如果相关的话，目前在家庭，父母，孩子表中唯一的是这些列:

If it's relevant, the only thing in the family, parent, child tables for now are these columns:

  t.string :content
  t.integer :user_id

推荐答案

您没有以下方法:

User.family.new
User.child.new

定义has_many关联时，只需使用以下方法来创建新的关联对象:

When you define has_many association, you just have these methods to create new object associated:

collection.build(attributes = {}, …)
collection.create(attributes = {})

遵循Rails指南:

集合被作为第一个参数传递的符号代替 has_many

collection is replaced with the symbol passed as the first argument to has_many

您可以查看 has_many关联参考以获得更多信息. 因此，如果User要创建新的家庭或孩子，则需要使用以下方法:

You can look at this has_many association reference for more info. So, If User want create new family or child, you need to use these methods:

user = User.create(name: "ABC") # create new user and save to database. 
user.families.build  # create new family belongs to user
user.children.build  # create new children belongs to user

user.families.create # create new family belongs to user and save it to database.
user.children.create # create new child belongs to user and save it to database.

如果您想让孩子属于属于家庭的父母，则可以修改您的关联:

If you want to get children belongs to parent which belongs to family, you can modify your association:

Class Family < ActiveRecord::Base

 belongs_to :user
 has_many :parents
 has_many :children, through: :parents # Get children through parents
end

Class Parent < ActiveRecord::Base

 belongs_to: :user
 belongs_to: :family
 has_many: :children

end

Class Child < ActiveRecord::Base

 belongs_to :user
 belongs_to :parent

end

现在，您可以使用以下方法获得所有属于一个家庭的父母的孩子(我支持家庭的ID = 1):

Now, you can get all children belongs to parents which belongs to a family ( I suppost family have id = 1) with:

 f = Family.find(1) # Find a family with id = 1
 f.children # Get all children in family.

这篇关于Rails:belongs_to多个>方法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！