blocks|key|4218589|text|如果你真的想这样做，那么这里将是一个开始挖掘的好地方：https://github.com/rails/rails/blob/ed7614aa7de2eaeba16c9af11cf09b4fd7ed6819/activemodel/lib/active_model/validations/validates.rb#L82|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4218590|然而，老实说，在ActiveModel内部，我不会用棍子戳。|4218591|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/rails/rails/blob/ed7614aa7de2eaeba16c9af11cf09b4fd7ed6819/activemodel/lib/active_model/validations/validates.rb#L82^0|R|3Q|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

If you really want to do this then here would be a good place to start digging: <a href="https://github.com/rails/rails/blob/ed7614aa7de2eaeba16c9af11cf09b4fd7ed6819/activemodel/lib/active_model/validations/validates.rb#L82" rel="nofollow">https://github.com/rails/rails/blob/ed7614aa7de2eaeba16c9af11cf09b4fd7ed6819/activemodel/lib/active_model/validations/validates.rb#L82</a>

However, to be honest, inside of ActiveModel is not where I'd be poking with a stick.

blocks|key|534919|text|如果您可以编辑原始模型上的约束以在其上放置:if+=>+:some_function，则可以轻松地更改它调用以返回false的函数的行为。我测试了一下，它很容易就能工作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|534920|class+Foo+<+ActiveRecord::Base

++validates+:field,+:presence+=>+true,+:if+=>+:stuff


++attr_accessor+:field

++def+stuff
++++++return+true;
++end

end|code-block|syntax|javascript|534921|然后在其他地方：|534922|Foo.class_eval+{
++def+stuff
++++false
++end
}|534923|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

If you can edit the constraint on the original model to put an :if => :some_function on it, you can easily change the behavior of the function it calls to return false. I tested this and it works pretty easily:

<pre><code>class Foo &lt; ActiveRecord::Base

 validates :field, :presence =&gt; true, :if =&gt; :stuff


 attr_accessor :field

 def stuff
 return true;
 end

end
</code></pre>

and then somewhere else:

<pre><code>Foo.class_eval {
 def stuff
 false
 end
}
</code></pre>

blocks|key|4218654|text|一种解决方案是扩展验证：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4218655|#no+need+of+instance_eval+just+open+the+class
class+Dummy+<+ActiveRecord::Base
++#validates+:field,+:presence+=>+true+

++def+self.validates(*attributes)
++++if+attributes.first+==+:field+#=>+add+condition+on+option+if+necessary
++++++return+#+don't+validate
++++else
++++++super(*attributes)+#let+normal+behavior+take+over
++++end
++end
end|code-block|syntax|javascript|4218656|不，这不是简单的修补，而是扩展或装饰行为。Rails+3.1是基于“多重继承”的思想构建的，带有模块包含，特别是为了允许这种敏捷性。|4218657|更新#2|4218658|需要注意的是，在gem包含对validates的调用之前，必须使用重新定义的validates方法加载该类。为此，在railsguides中建议的"rails/all“之后，需要config/application.rb中的文件。大概是这样的：|offset|length|4218659|require+File.expand_path('../boot',+__FILE__)

require+'rails/all'+#+this+where+rails+(including+active_record)+is+loaded
require+File.expand_path('../dummy'+__FILE__)+#or+wherever+you+want+it

#this+is+where+the+gems+are+loaded...
#+the+most+important+is+that+active_record+is+loaded+before+dummy+but...
#+not+after+the+gem+containing+the+call+to+validate+:field
if+defined?(Bundler)
++Bundler.require+*Rails.groups(:assets+=>+%25w(development+test))
end|4218660|希望它现在可以工作了！|4218661|entityMap|0|LINK|mutability|MUTABLE|url|http://guides.rubyonrails.org/configuring.html#running-code-before-rails^0|0|0|0|0|1M|B|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|13|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|14|8|@]|9|@$M|15|N|16|1|17]]|A|$]]|$1|O|3|P|5|D|7|18|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|19|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

One solution is to extend validates :
<pre><code>#no need of instance_eval just open the class
class Dummy &lt; ActiveRecord::Base
 #validates :field, :presence =&gt; true 

 def self.validates(*attributes)
 if attributes.first == :field #=&gt; add condition on option if necessary
 return # don't validate
 else
 super(*attributes) #let normal behavior take over
 end
 end
end
</code></pre>
And no that's not monkey-patching but extending or decorating a behavior. Rails 3.1 is built on the idea of &quot;multi- inheritance&quot; with module inclusion, specifically to allow this kind agility.
<h1>update #2</h1>
One caveat is you must load the class with the redefined validates method before the gem containing the call to validates. To do so, require the file in config/application.rb after require &quot;rails/all&quot; as suggested in the <a href="http://guides.rubyonrails.org/configuring.html#running-code-before-rails" rel="nofollow noreferrer">railsguides</a>. Something like that :
<pre><code>require File.expand_path('../boot', __FILE__)

require 'rails/all' # this where rails (including active_record) is loaded
require File.expand_path('../dummy' __FILE__) #or wherever you want it

#this is where the gems are loaded...
# the most important is that active_record is loaded before dummy but...
# not after the gem containing the call to validate :field
if defined?(Bundler)
 Bundler.require *Rails.groups(:assets =&gt; %w(development test))
end
</code></pre>
Hope it works now!

blocks|key|2603804|text|我必须更深入地查看代码和帮助，但我认为有可能检查类的验证器列表，然后修改要更改的验证条目，以便在其中添加:if+=>+:some_function条件。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2603805|对于生产来说，你只需要做一次(这样它就可以放在一个初始化器中，但是对于开发，你需要把它放在模型中，或者放在每次加载相应模型(可能是观察者？)的其他地方)。|2603806|(在对答案进行研究时，我将使用更多信息来编辑答案。)|2603807|entityMap^0|1G|L|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|O|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|P|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|K|$]]

I'd have to look more into the code and help, but I'm thining it might be possible to inspect the list of validators of the class, and then modify the entry for the validation you want to change to add in an <code>:if =&gt; :some_function</code> conditional to it. 

You'll need to do it only once for production (so it can be put inside an initializer, but for development you'll need to put it in the model, or somewhere else that will get loaded each time the corresponding model is (perhaps an observer?).

(I'll edit the answer with more information as I come to research it.)

blocks|key|532163|text|为什么不使用@dummy.save_without_validation方法完全跳过验证呢？我更喜欢这样做：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|532164|if+@dummy.valid?
++@dummy.save+#+no+problem+saving+a+valid+record
else
++if+@dummy.errors.size+==+1+and+@dummy.errors.on(:field)
++++#+skip+validations+b/c+we+have+exactly+one+error+and+it+is+the+validation+that+we+want+to+skip
++++@dummy.save_without_validation+
++end
end|code-block|syntax|javascript|532165|您可以将此代码放入模型或控制器中，具体取决于您的需要。|532166|entityMap^0|6|U|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

Why not use <code>@dummy.save_without_validation</code> method to skip validations altogether? I prefer do something like this:

<pre><code>if @dummy.valid?
 @dummy.save # no problem saving a valid record
else
 if @dummy.errors.size == 1 and @dummy.errors.on(:field)
 # skip validations b/c we have exactly one error and it is the validation that we want to skip
 @dummy.save_without_validation 
 end
end
</code></pre>

You could put this code in your model or in the controller, depending on your needs.

blocks|key|2603881|text|我遇到了类似的问题，并能够使用以下命令克服它：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2603882|class+MyModel+<<+Dummy
++#+erase+the+validations+defined+in+the+plugin/gem+because+they+interfere+with+our+own
++Dummy.reset_callbacks(:validate)
++...
end|code-block|syntax|javascript|2603883|这是在Rails+3.0下实现的。注意:它确实删除了所有验证，所以如果您想保留其他验证，可以尝试Dummy.skip_callback(...)，但我找不出正确的参数咒语来使其工作。|offset|length|style|CODE|2603884|entityMap^0|0|0|1C|O|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I had a similar problem and was able to get past it using:

<pre><code>class MyModel &lt;&lt; Dummy
 # erase the validations defined in the plugin/gem because they interfere with our own
 Dummy.reset_callbacks(:validate)
 ...
end
</code></pre>

This is under Rails 3.0. The caveat: It does remove ALL validations, so if there are others you want to keep you could try <code>Dummy.skip_callback(...)</code>, but I could not figure out the right incantation of arguments to make that work.

blocks|key|4218841|text|假设Dummy的原始实现是在引擎中定义的，那么就会有一个令人讨厌的黑客攻击，它会做你想做的事情。在应用程序中定义Dummy，以防止Dummy的原始实现被自动加载。然后将源代码加载到Dummy并删除执行验证的代码行。评估修改后的源代码。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4218842|将以下内容放入您的应用程序/model/dummy.rb|4218843|class+Dummy+<+ActiveRecord::Base
end

#+Replace+DummyPlugin+with+name+of+engine
engine+=+Rails::Application::Railties.engines.find+{+%7Ce%7C+e.class+==+DummyPlugin::Engine+}
dummy_source+=+File.read+File.join(engine.config.root,+"app",+"models",+"dummy.rb")
dummy_source+=+dummy_source.gsub(/validates+:field,+:presence+=>+true.*/,+"")
eval+dummy_source|code-block|syntax|javascript|4218844|如果它是常规的gem而不是引擎，同样的概念也适用，只需要从gem根而不是引擎根加载Dummy的源代码。|4218845|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Assuming the original implementation of Dummy is defined in an engine there is a nasty hack that will do what you want. Define Dummy in your application to keep the original implementation of Dummy from being auto-loaded. Then load the source to Dummy and remove the line that does the validation. Eval the modified source.

Put the following in your app/models/dummy.rb

<pre><code>class Dummy &lt; ActiveRecord::Base
end

# Replace DummyPlugin with name of engine
engine = Rails::Application::Railties.engines.find { |e| e.class == DummyPlugin::Engine }
dummy_source = File.read File.join(engine.config.root, "app", "models", "dummy.rb")
dummy_source = dummy_source.gsub(/validates :field, :presence =&gt; true.*/, "")
eval dummy_source
</code></pre>

If it is regular gem instead of an engine the same concept would apply, just would need to load the source for Dummy from the gem root instead of the engine root.

blocks|key|4218904|text|我找到了一个解决方案，不确定它有多可靠，但它在我的情况下工作得很好。@aVenger实际上与他的答案很接近。只是_validators访问器只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。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4218905|Dummy.class_eval+do
++_validators.reject!{+%7Ckey,+_%7C+key+==+:field+}

++_validate_callbacks.reject!+do+%7Ccallback%7C
++++callback.raw_filter.attributes+==+[:field]
++end
end|code-block|syntax|javascript|4218906|这将删除:field的所有验证器。如果您想要更精确，可以拒绝特定的_validators验证器，该验证器与验证回调的raw_filter访问器相同。|4218907|entityMap^0|1K|B|2R|J|3I|M|0|0|4|6|X|B|1M|A|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|N|$]]

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 <code>_validators</code> accessor contains only information used for reflection, but not the actual validator callbacks! They are contained in the <code>_validate_callbacks</code> accessor, not to be confused with <code>_validations_callbacks</code>.

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

 _validate_callbacks.reject! do |callback|
 callback.raw_filter.attributes == [:field]
 end
end
</code></pre>

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

blocks|key|532257|text|当您在一行中声明多个属性的验证时，Answer+by+aVenger会出现问题：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|532258|validates+:name,+:message,+:presence+=>+true|code-block|syntax|javascript|532259|这是因为这一行在attributes过滤器中创建了一个具有多个属性的raw_filter：|532260|Model.send(:_validate_callbacks)
=>+[#<ActiveSupport::Callbacks::Callback:0xa350da4+@klass=Model(...),+...+,+@raw_filter=#<ActiveModel::Validations::PresenceValidator:0x9da7470+@attributes=[:name,+:message],+@options={}>,+@filter="_callback_before_75",+@compiled_options="true",+@callback_id=76>]|532261|我们必须从该数组中删除所需的属性，并拒绝不带属性的回调|532262|Dummy.class_eval+do

++_validators.reject!{+%7Ckey,+_%7C+key+==+:field+}

++_validate_callbacks.each+do+%7Ccallback%7C
++++callback.raw_filter.attributes.delete+:field
++end

++_validate_callbacks.reject!+do+%7Ccallback%7C
++++callback.raw_filter.attributes.empty?+%7C%7C+
++++++callback.raw_filter.attributes+==+[:field]
++end
end|532263|我已经在Rails+3.2.11应用程序上实现了这个功能。|532264|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

Answer by aVenger has problems when you declare validations of more than one attribute in a line:

<pre class="lang-rb prettyprint-override"><code>validates :name, :message, :presence =&gt; true
</code></pre>

That's because this line creates a raw_filter with more than one attribute in attributes filter:

<pre class="lang-rb prettyprint-override"><code>Model.send(:_validate_callbacks)
=&gt; [#&lt;ActiveSupport::Callbacks::Callback:0xa350da4 @klass=Model(...), ... , @raw_filter=#&lt;ActiveModel::Validations::PresenceValidator:0x9da7470 @attributes=[:name, :message], @options={}&gt;, @filter="_callback_before_75", @compiled_options="true", @callback_id=76&gt;]
</code></pre>

We have to delete the desired attribute from that array and reject the callbacks without attributes

<pre><code>Dummy.class_eval do

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

 _validate_callbacks.each do |callback|
 callback.raw_filter.attributes.delete :field
 end

 _validate_callbacks.reject! do |callback|
 callback.raw_filter.attributes.empty? || 
 callback.raw_filter.attributes == [:field]
 end
end
</code></pre>

I have this working on a Rails 3.2.11 app.

blocks|key|535095|text|当我试图这样做时，为了从spree地址模型中删除手机验证，下面是我开始工作的代码。我添加了callback.raw_filter的类型检查，因为我只想删除phone字段上的在线状态验证器。我还必须添加它，因为它在尝试对Spree::Address模型中指定的其他验证器之一运行时会失败，该验证器没有callback.raw_filter的“attributes”键，因此抛出了异常。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|535096|Spree::Address.class_eval+do

+++#+Remove+the+requirement+on+:phone+being+present.
++_validators.reject!{+%7Ckey,+_%7C+key+==+:phone+}

++_validate_callbacks.each+do+%7Ccallback%7C
++++callback.raw_filter.attributes.delete+:phone+if+callback.raw_filter.is_a?(ActiveModel::Validations::PresenceValidator)
++end

end|code-block|syntax|javascript|535097|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

As I was trying to do this to remove the phone validation from the spree Address model, below is the code I got to work. I added the type check for callback.raw_filter because I only wanted to remove the presence validator on the phone field. I also had to add it because it would fail when trying to run against one of the other validators specified in the Spree::Address model that did not have an 'attributes' key for callback.raw_filter, thus an exception was thrown.

<pre><code>Spree::Address.class_eval do

 # Remove the requirement on :phone being present.
 _validators.reject!{ |key, _| key == :phone }

 _validate_callbacks.each do |callback|
 callback.raw_filter.attributes.delete :phone if callback.raw_filter.is_a?(ActiveModel::Validations::PresenceValidator)
 end

end
</code></pre>

blocks|key|535110|text|在Rails+4.1中，|type|unstyled|depth|inlineStyleRanges|entityRanges|data|535111|我可以做_validate_callbacks.clear。在我的例子中，我希望删除gem的所有验证，这样我就可以创建自己的验证。我在一个模块中做到了这一点，这个模块被打到了类中。|535112|Module+#Name
+++extend+ActiveSupport::Concern
+++included+do
++++++++_validate_callbacks.clear
++++++++#add+your+own+validations+now
+++end
end|code-block|syntax|javascript|535113|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

In Rails 4.1,

I was able to do _validate_callbacks.clear. In my case, I wanted all the validations for a gem removed, so I could create my own. I did this in a module that was patched into the class.

<pre><code>Module #Name
 extend ActiveSupport::Concern
 included do
 _validate_callbacks.clear
 #add your own validations now
 end
end
</code></pre>

blocks|key|2604144|text|我认为这是目前最实际的解决方案(我使用的是rails+4.1.6)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2604145|#+Common+ninja
class+Ninja+<+ActiveRecord::Base
++validates+:name,+:martial_art,+presence:+true
end

#+Wow!+He+has+no+martial+skills
Ninja.class_eval+do
++_validators[:martial_art]
++++.find+{+%7Cv%7C+v.is_a?+ActiveRecord::Validations::PresenceValidator+}
++++.attributes
++++.delete(:martial_art)
end|code-block|syntax|javascript|2604146|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I think this is the most actual solution at this moment (I'm using rails 4.1.6):

<pre><code># Common ninja
class Ninja &lt; ActiveRecord::Base
 validates :name, :martial_art, presence: true
end

# Wow! He has no martial skills
Ninja.class_eval do
 _validators[:martial_art]
 .find { |v| v.is_a? ActiveRecord::Validations::PresenceValidator }
 .attributes
 .delete(:martial_art)
end
</code></pre>

blocks|key|4503320|text|删除所有验证的最简单方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4503321|clear_validators!|code-block|syntax|javascript|4503322|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Easest way to remove all validations:

<pre><code>clear_validators!
</code></pre>

blocks|key|535160|text|如果您不想在父类中进行任何更改，则首先清除子类中的所有验证，并将所有必需的验证从父类复制到子类|type|unstyled|depth|inlineStyleRanges|entityRanges|data|535161|++class+Dummy+<+ActiveRecord::Base
++++++validates+:property,+presence:+true
++++++validates+:value,+length:+{+maximum:+255+}
++end|code-block|syntax|javascript|535162|并在子类中重写它|535163|Dummy.class_eval+do++++
++clear_validators!
++validates+:property,+presence:+true
end|535164|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

If you doesn't want to make any changes in Parent class then first clear all validations in child class and copy all required validation from parent class to child class

<pre><code> class Dummy &lt; ActiveRecord::Base
 validates :property, presence: true
 validates :value, length: { maximum: 255 }
 end
</code></pre>

And override it in child class

<pre><code>Dummy.class_eval do 
 clear_validators!
 validates :property, presence: true
end
</code></pre>

blocks|key|4503389|text|我想补充的是，如果您试图清除模型实例(而不是整个模型类)上的验证，请不要执行my_dummy._validate_callbacks.clear，因为这将清除模型类的每个实例(以及未来实例)上的验证。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|CODE|entityRanges|data|4503390|仅对于该实例(如果您希望稍后恢复验证)，请尝试以下操作：|4503391|创建验证回调的副本(如果您希望稍后恢复)：将您的回调实例上的验证回调设置为my_dummy_validate_callbacks+=+my_dummy._validate_callbacks.clone|4503392|Set：my_dummy._validate_callbacks+=+{}|unordered-list-item|4503393|
|4503394|Do+what+you+want+on+|4503395|4503396|：my_dummy._validate_callbacks+=+{}|4503397|4503398|Do+what+you+want+on+my_dummy+validation+callbacks：|4503399|4503400|entityMap^0|J|8|27|G|12|Y|0|0|11|1S|0|4|X|0|0|0|0|1|X|0|0|K|8|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|D]]|E|@]|F|$]]|$1|G|3|H|5|6|7|17|8|@]|E|@]|F|$]]|$1|I|3|J|5|6|7|18|8|@$9|19|A|1A|B|D]]|E|@]|F|$]]|$1|K|3|L|5|M|7|1B|8|@$9|1C|A|1D|B|D]]|E|@]|F|$]]|$1|N|3|O|5|6|7|1E|8|@]|E|@]|F|$]]|$1|P|3|Q|5|M|7|1F|8|@]|E|@]|F|$]]|$1|R|3|O|5|6|7|1G|8|@]|E|@]|F|$]]|$1|S|3|T|5|M|7|1H|8|@$9|1I|A|1J|B|D]]|E|@]|F|$]]|$1|U|3|O|5|6|7|1K|8|@]|E|@]|F|$]]|$1|V|3|W|5|M|7|1L|8|@$9|1M|A|1N|B|D]]|E|@]|F|$]]|$1|X|3|-4|5|6|7|1O|8|@]|E|@]|F|$]]|$1|Y|3|-4|5|6|7|1P|8|@]|E|@]|F|$]]]|Z|$]]

Wanted to add that, if you're trying to clear validations on a instance of your Model (not the entire model class), don't do <code>my_dummy._validate_callbacks.clear</code>, as that will clear validations on every instance (and future instance) of your <code>Dummy</code> model class.

For just the instance (and if you wanted to reinstate the validations later), try the following:

<ol>
<li>Create a copy of the validate callbacks (if you want to reinstate later):
<code>my_dummy_validate_callbacks = my_dummy._validate_callbacks.clone</code></li>
<li>Set the validate callbacks on your instance to empty:
<code>my_dummy._validate_callbacks = {}</code></li>
<li>Do what you want on <code>my_dummy</code> validation free!</li>
<li>Reinstate the callbacks: <code>my_dummy._validate_callbacks = my_dummy_validate_callbacks</code></li>
</ol>

blocks|key|535228|text|对于rails+4.2+(~+5.0)，它可以通过一个方法使用以下模块：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|535229|module+ValidationCancel
+++def+cancel_validates+*attributes
++++++attributes.select+{%7Cv%7C+Symbol+===+v+}.each+do+%7Cattr%7C
+++++++++self._validators.delete(+attr+)

+++++++++self._validate_callbacks.select+do+%7Ccallback%7C
++++++++++++callback.raw_filter.try(+:attributes+)+==+[+attr+]+;end
+++++++++.each+do+%7Cvc%7C
++++++++++++self._validate_callbacks.delete(+vc+)+;end+;end+;end+;end|code-block|syntax|javascript|535230|注意:由于过滤器可以是一个关联的符号，也可以是一个特定的验证器，所以我们必须使用#try。|offset|length|style|CODE|535231|然后我们可以在类声明中使用rails友好的形式：|535232|class+Dummy
+++extend+ValidationCancel
+++cancel_validates+:field+;end|535233|注意:由于移除验证器会在全局范围内影响整个类及其后代，因此不建议使用该验证器来移除验证器，而是为具体规则添加if子句，如下所示：|535234|module+ValidationCancel
+++def+cancel_validates+*attributes
++++++this+=+self
++++++attributes.select+{%7Cv%7C+Symbol+===+v+}.each+do+%7Cattr%7C
+++++++++self._validate_callbacks.select+do+%7Ccallback%7C
++++++++++++callback.raw_filter.try(+:attributes+)+==+[+attr+]+;end
+++++++++.each+do+%7Cvc%7C
++++++++++++ifs+=+vc.instance_variable_get(+:@if+)
++++++++++++ifs+<<+proc+{+!+self.is_a?(+this+)+}+;end+;end+;end+;end|535235|这将限制执行指定类及其子类的验证回调。|535236|entityMap^0|0|0|14|4|0|0|0|1I|2|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|10|8|@$I|11|J|12|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|13|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|14|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|15|8|@$I|16|J|17|K|L]]|9|@]|A|$]]|$1|S|3|T|5|D|7|18|8|@]|9|@]|A|$E|F]]|$1|U|3|V|5|6|7|19|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|X|$]]

For rails 4.2 (~ 5.0) it can be used the following module with a method:

<pre><code>module ValidationCancel
 def cancel_validates *attributes
 attributes.select {|v| Symbol === v }.each do |attr|
 self._validators.delete( attr )

 self._validate_callbacks.select do |callback|
 callback.raw_filter.try( :attributes ) == [ attr ] ;end
 .each do |vc|
 self._validate_callbacks.delete( vc ) ;end ;end ;end ;end
</code></pre>

Note: Since the filtern can be a symbol of an association, or a specific validator, so we have to use <code>#try</code>.

Then we can use rails-friendly form in a class declaration:

<pre><code>class Dummy
 extend ValidationCancel
 cancel_validates :field ;end
</code></pre>

Note: since removal of the validator is affecting to the whole class and its descendants globally, it is not recommended to use it to remove validations in such way, instead add <code>if</code> clause for the specific rule as follows:

<pre><code>module ValidationCancel
 def cancel_validates *attributes
 this = self
 attributes.select {|v| Symbol === v }.each do |attr|
 self._validate_callbacks.select do |callback|
 callback.raw_filter.try( :attributes ) == [ attr ] ;end
 .each do |vc|
 ifs = vc.instance_variable_get( :@if )
 ifs &lt;&lt; proc { ! self.is_a?( this ) } ;end ;end ;end ;end
</code></pre>

This restricts execution of the validation callback for the specified class and its descendants.

blocks|key|4503478|text|每个Rails验证器，无论是预定义的还是自定义的，都是一个对象，并被期望响应#validate(record)方法。您可以对此方法进行补丁或存根。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4503479|#+MyModel.validators_on(:attr1,+:attr2,+...)+is+also+useful
validator+=+MyModel.validators.detect+do+%7Cv%7C
++validator_i_am_looking_for?(v)
end

def+validator.validate(*_)
++true
end

#+In+RSpec+you+can+also+consider:
allow(validator).to+receive(:validate).and_return(true)|code-block|syntax|javascript|4503480|在Rails+5.1中进行了测试。|4503481|除非你明白自己在做什么，否则不要这么做;)|4503482|entityMap^0|12|H|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|V|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

Every Rails validator, pre-defined or custom, is an object, and is expected to respond to <code>#validate(record)</code> method. You can monkey patch or stub this method.

<pre><code># MyModel.validators_on(:attr1, :attr2, ...) is also useful
validator = MyModel.validators.detect do |v|
 validator_i_am_looking_for?(v)
end

def validator.validate(*_)
 true
end

# In RSpec you can also consider:
allow(validator).to receive(:validate).and_return(true)
</code></pre>

Tested in Rails 5.1.

Don't do this unless you understand what you're doing ;)

blocks|key|2604385|text|这并没有直接回答这个问题，但在这种情况下，您应该考虑以下选项:您可以在before_validation挂钩中设置必需的字段，而不是禁用验证。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2604386|因为您不需要这些必填字段，所以使用一些满足验证的虚拟数据来设置它们，然后忘记它们。|2604387|没有丑陋的猴子补丁。|2604388|entityMap^0|Z|H|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|O|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|P|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|K|$]]

This does not directly answer the question but here's an option you should consider in such a situation: instead of disabling validation, you could set the required fields in a <code>before_validation</code> hook.

Since you don't need those required fields, set them with some dummy data that satisfies the validation and forget about them.

No ugly monkey patching.

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

<pre><code>class Dummy &lt; ActiveRecord::Base
 validates :field, :presence =&gt; true 
end
</code></pre>

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

<pre><code>Dummy.instance_eval do
 ...
end
</code></pre>

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.

Edit #1

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.

How to remove validation using instance_eval clause in Rails?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我想使用instance_eval来增强现有的类。原始定义包含验证，它要求存在某些字段，例如：class Dummy < ActiveRecord::Base validates :field, :presence => true end现在，我想使用instance_eval (或任何其他方法，实际上)将其更改为o...

问如何在Rails中删除使用instance_eval子句的验证？
EN

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问如何在Rails中删除使用instance_eval子句的验证？EN