如何在Rails中使用instance_eval子句删除验证？ [英] How to remove validation using instance_eval clause in Rails?

问题描述

我想使用instance_eval增强现有的类。原始定义包含验证，该验证要求存在某些字段，即：

I would like to enhance existing class using instance_eval. There original definition contains validation, which require presence of certain fields, ie:

class Dummy < ActiveRecord::Base
  validates :field, :presence => true 
end

现在，我想使用instance_eval（或任何其他方法）将其更改为可选，真的）：

Now I want to change that to optional using instance_eval (or any other method, really):

Dummy.instance_eval do
  ...
end

删除验证的正确语法是什么，因此该字段是可选的。我宁愿直接在模型层上执行此操作，而不是在控制器或视图中执行奇怪的操作。并不是真正需要使用instance_eval，但是据我所知，这通常是在Rails中增强类的最佳方法。

What would be the proper syntax to remove the validation, so the field is optional. I would rather do this directly on the model layer, instead doing weird hacks in controllers or views. The use of instance_eval is not really required, but as far as I know, this is generally the best way to enhance classes in Rails.

编辑＃1

通常-原始类是gem的一部分，我不想分叉它，也不想绑定到特定版本。一般原因并不重要。简单地编辑原始模型比猴子修补的后果要糟得多。

In general - the original class is part of the gem and I don't want to fork it, nor tie to specific release. The general cause is not really important. Simply editing the original model has far worse consequences than monkey patching.

推荐答案

我找到了一个解决方案，不确定它的可靠性如何，但是对我来说效果很好。 @aVenger实际上很接近他的答案。只是 _validators 访问器仅包含用于反射的信息，而不包含实际的验证器回调！它们包含在 _validate_callbacks 访问器中，不要与 _validations_callbacks 混淆。

I found a solution, not sure how solid it is, but it works well in my case. @aVenger was actually close with his answer. It's just that the _validators accessor contains only information used for reflection, but not the actual validator callbacks! They are contained in the _validate_callbacks accessor, not to be confused with _validations_callbacks.

Dummy.class_eval do
  _validators.reject!{ |key, _| key == :field }

  _validate_callbacks.reject! do |callback|
    callback.raw_filter.attributes == [:field]
  end
end

这将删除：field 的所有验证器。如果要更精确，可以拒绝 _validators 的特定验证器，该验证器与 raw_filter 访问器相同验证回调的数量。

This will remove all validators for :field. If you want to be more precise, you can reject the specific validator for _validators which is the same as the raw_filter accessor of validate callbacks.

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