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面试准备

Ruby On Rails 面试题与答案

Answer: Polymorphic associations allow a model to belong to more than one other model through a single association.

class Picture < ActiveRecord::Base

belongs_to : imageable, polymorphic: true

end

class Employee < ActiveRecord::Base

has_many : pictures, as: : imageable

end

class Product < ActiveRecord::Base

has_many : pictures, as: : imageable

end

Here, the class Picture belongs_to both Employee and Product, but does so through a single association rather than through multiple.
Be sure to know an appropriate situation to create a polymorphic association, such as creating a comment model associated with multiple other models (articles, photos, etc.). The advantage of using polymorphism here is that it allows you to create a single comment model, rather than separate models for each one (PhotoComment model, ArticleComment model, etc.)

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