如何向 ActiveRecord 添加新属性 [英] How to add new attribute to ActiveRecord

问题描述

从模型中获取所有值后，我想向 ActiveRecord 类添加另一个自定义属性(此属性不是 db 中的列)，以便我可以在视图中使用它，但 Rails 不允许我添加一个.我应该在它的模型类中添加什么?

After getting all values from model, I want to add another custom attribute to the ActiveRecord class (this attribute is not a column in db) so that I could use it in view, but rails does not allow me to add one. What should I add in its model class?

@test.all

@test.each do |elm|
    elm[:newatt] = 'added string'
end

错误:

can't write unknown attribute `newatt'

推荐答案

试试这个

class Test < ActiveRecord::Base
  attr_accessor :newattr
end

你可以像访问它

@test = Test.new
@test.newattr = "value"

您可能会注意到这是一个属性，而不是哈希.所以它使用 . 语法.但是，如果您需要它像散列一样运行，您可以在不定义新属性的情况下执行此操作

As you may notice this a property, not a hash. so it uses . syntax. however, if you need it to behave like an hash you can do this without defining a new attribute

@test.all
@test.each do |elm|
    new_elm = {}
    new_elm[:newatt] = 'added string'
end

最后，我不确定您要做什么.如果这对您来说没有意义，请重新表述您的问题，以便我们更好地理解问题.

Lastly, I am not exactly sure what you are trying to do. if this doesn't make sense to you, kindly rephrase your question so we can understand the problem better.

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