Rails的控制台复杂的查询

Question

我想用后续查询这样张贴子类别：

Gender.where(gender: 'Masc').categories.where(name: 'clothes').subcategories.create([{ name: 't-shirt' }]) 

，但显示这个错误！

rake aborted! NoMethodError: undefined method `subcategories' for Category

我搜索了但无法找到如何使用链接查询创建数据。

Gender Model: 

class Gender < ActiveRecord::Base 
    extend FriendlyId 
    friendly_id :gender, use: [:slugged, :history] 

    has_many :categories 
    has_many :subcategories, through: :categories 
    has_many :products 
    accepts_nested_attributes_for :categories 
    accepts_nested_attributes_for :products 
    accepts_nested_attributes_for :subcategories 
    attr_accessible :gender, :categories_attributes, :subcategories_attributes, 


end 

Answer 1

where(name: 'clothes')返回查询，而不是模型实例。据推测，您的类别中有has_many :subcategories，类别名称是唯一的，因此您可以使用find_by来查找衣服类别，然后在该类别上调用subcategories。同样，对于查找性别：

Gender.find_by(gender: 'Masc') # This gives you a single Gender instance 
     .categories 
     .find_by(name: 'clothes') # and then a single Category here 
     .subcategories 
     .create(name: 't-shirt')