Model 当值不为 nil 时获取的属性为 Nil

Question

If I set a value for a model attribute, it is saved correctly.

I have a model

# gem 'rails', '6.1.3'
class Start < ApplicationRecord

end


 s = Start.find(465860)
 s.gear_change = 'test value'
 s.save!
 s.gear_change
 => nil
 s
=> #<Start id: 465860, gear_change: "test value">

Why is rails returning nil?

Answer 1

There could be another column called gear in your database. And gear_change could be the Active Record dirty method being called on the gear attribute. Since the gear attribute has not changed, the gear_change dirty method returns nil .

One solution would be to access the gear_change attribute as a hash value - s[:gear_change] or s['gear_change'] .

Answer 2

It is possible that you have overridden the gear_change method in your model somewhere which is returning nil .