Rails驗證 - 在創建子模型時驗證父模型

Question

假設我有ParentModel has_many ChildModel。

有沒有一種方法來檢查（驗證）ParentModel而創建子（例如像檢查是否具有相同名稱的子記錄存在？

Answer 1

這是非常簡單的，如有錯誤指正。

def Parent 
    has_many :children 
end 
def Child 
    belongs_to :parent 
    #Here you could run some validations, for example: 
    validates :name,presence: true, length: { minimum: 1 },uniqueness: { scope: :parent_id } 
    #by running uniqueness with scope, you can repeat names, but not associated with the same parent. 
end 

那麼可以，例如：

p = Parent.first #suppose we already have the parent 
p.child.new #create a child, with attributes if needed 
p.valid? #p won't be valid unless his new child is 

替代：

p = Parent.first #suppose we already have the parent 
c = Child.new #create a child, with attributes if needed 
p.children << C#append the child to the collection, if C is invalid, then it won't be saved into the database 
p.valid? #validate,