blocks|key|1499869|text|从Ruby2.3.0开始，您可以将安全导航操作符(&.)与Numeric#nonzero?结合使用。如果实例为nil，则&.返回nil；如果实例数为0，则返回nonzero?|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1499870|unless+val&.nonzero?
++#+Is+nil+or+zero
end|code-block|syntax|javascript|1499871|或后缀：|1499872|do_something+unless+val&.nonzero?|1499873|entityMap|0|LINK|mutability|MUTABLE|url|http://ruby-doc.org/core-2.3.0/Numeric.html#method-i-nonzero-3F^0|P|2|T|G|1J|3|1O|2|1S|3|22|1|27|8|T|G|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]|$9|17|A|18|B|C]|$9|19|A|1A|B|C]]|D|@$9|1B|A|1C|1|1D]]|E|$]]|$1|F|3|G|5|H|7|1E|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1F|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|1G|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|1H|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

From Ruby 2.3.0 onward, you can combine the safe navigation operator (<code>&amp;.</code>) with <a href="http://ruby-doc.org/core-2.3.0/Numeric.html#method-i-nonzero-3F" rel="noreferrer"><code>Numeric#nonzero?</code></a>. <code>&amp;.</code> returns <code>nil</code> if the instance was <code>nil</code> and <code>nonzero?</code> - if the number was <code>0</code>:

<pre><code>unless val&amp;.nonzero?
 # Is nil or zero
end
</code></pre>

Or postfix:

<pre><code>do_something unless val&amp;.nonzero?
</code></pre>

blocks|key|1499356|text|首先，我认为这是您可以检查特定条件的最简洁的方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1499357|其次，对我来说，这是一种代码气味，表明您的设计中存在潜在的缺陷。通常情况下，nil和零不应该意味着相同的事情。如果可能，您应该尝试在执行此代码之前消除val为nil的可能性，无论是通过在方法的开头进行检查，还是通过某种其他机制。|1499358|您可能有一个完全合法的理由这样做，在这种情况下，我认为您的代码是好的，但如果可能的话，我至少会考虑取消nil检查。|1499359|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

First off I think that's about the most concise way you can check for that particular condition.

Second, to me this is a code smell that indicates a potential flaw in your design. Generally nil and zero shouldn't mean the same thing. If possible you should try to eliminate the possibility of val being nil before you hit this code, either by checking that at the beginning of the method or some other mechanism.

You might have a perfectly legitimate reason to do this in which case I think your code is good, but I'd at least consider trying to get rid of the nil check if possible.

blocks|key|1499408|text|你可以使用Object.nil吗？专门测试nil+(而不是陷入false和nil之间)。你也可以将一个方法嵌入到对象中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1499409|class+Object
+++def+nil_or_zero?
+++++return+(self.nil?+or+self+==+0)
+++end
end

my_object+=+MyClass.new
my_object.nil_or_zero?
==>+false|code-block|syntax|javascript|1499410|不建议这样做，因为对对象的更改很难被同事跟踪，并且可能会使其他人无法预测您的代码。|1499411|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

You can use the Object.nil? to test for nil specifically (and not get caught up between false and nil). You can monkey-patch a method into Object as well. 

<pre><code>class Object
 def nil_or_zero?
 return (self.nil? or self == 0)
 end
end

my_object = MyClass.new
my_object.nil_or_zero?
==&gt; false
</code></pre>

This is not recommended as changes to Object are difficult for coworkers to trace, and may make your code unpredictable to others.

blocks|key|1714758|text|nil.to_i返回零，所以我经常这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1714759|val.to_i.zero?|code-block|syntax|javascript|1714760|然而，如果val是一个不respond_to+#to_i的对象，你会得到一个异常。|1714761|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

nil.to_i returns zero, so I often do this:

<pre><code>val.to_i.zero?
</code></pre>

However, you will get an exception if val is ever an object that does not respond_to #to_i.

blocks|key|1500059|text|我的解决方案也使用了细化，去掉了条件语句。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1500060|module+Nothingness
++refine+Numeric+do
++++alias_method+:nothing?,+:zero?
++end

++refine+NilClass+do
++++alias_method+:nothing?,+:nil?
++end
end

using+Nothingness

if+val.nothing?
++#+Do+something
end|code-block|syntax|javascript|1500061|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|$]]

My solution also use Refinements, minus the conditionals.

<pre><code>module Nothingness
 refine Numeric do
 alias_method :nothing?, :zero?
 end

 refine NilClass do
 alias_method :nothing?, :nil?
 end
end

using Nothingness

if val.nothing?
 # Do something
end
</code></pre>

blocks|key|1499495|text|Rails通过属性查询方法做到这一点，其中除了false和nil之外，0和"“也计算为false。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1499496|if+(model.attribute?)+#+=>+false+if+attribute+is+0+and+model+is+an+ActiveRecord::Base+derivation|code-block|syntax|javascript|1499497|然而，它也有它的批评者。http://www.joegrossberg.com/archives/002995.html|offset|length|1499498|entityMap|0|LINK|mutability|MUTABLE|url|http://www.joegrossberg.com/archives/002995.html^0|0|0|C|1C|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]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

Rails does this via attribute query methods, where in addition to false and nil, 0 and "" also evaluate to false. 

<pre><code>if (model.attribute?) # =&gt; false if attribute is 0 and model is an ActiveRecord::Base derivation
</code></pre>

However it has its share of detractors. <a href="http://www.joegrossberg.com/archives/002995.html" rel="nofollow noreferrer">http://www.joegrossberg.com/archives/002995.html</a>

blocks|key|1499902|text|简短明了|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1499903|[0,+nil].include?(val)|offset|length|style|CODE|1499904|entityMap^0|0|0|M|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

Short and clear

<code>[0, nil].include?(val)</code>

blocks|key|1499968|text|最短和最好的方法应该是|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1499969|if+val&.>(0)
++#+do+something
end|code-block|syntax|javascript|1499970|对于val&.>(0)，当val为nil时，它返回nil，因为>基本上也是一个方法，在ruby中nil等于false。当为val+==+0时，它返回false。|offset|length|style|CODE|1499971|entityMap^0|0|0|2|9|1P|8|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]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

Shortest and best way should be 

<pre><code>if val&amp;.&gt;(0)
 # do something
end
</code></pre>

For <code>val&amp;.&gt;(0)</code>
it returns nil when val is nil since > basically is also a method, nil equal to false in ruby. It return false when <code>val == 0</code>.

blocks|key|1499548|text|我通过定义一个"is?“来处理这个问题。方法，然后我可以在不同的类上不同地实现它。那么对于Array来说，"is?“意思是"size>0"；对于Fixnum，它意味着"self+!=+0"；对于String，它意味着"self+!=+''“。当然，NilClass定义了"is?“返回nil。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1499549|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I deal with this by defining an "is?" method, which I can then implement differently on various classes. So for Array, "is?" means "size>0"; for Fixnum it means "self != 0"; for String it means "self != ''". NilClass, of course, defines "is?" as just returning nil.

blocks|key|1499629|text|如果您愿意，您可以使用case：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1499630|+case+val+with+nil,+0
++++++#+do+stuff
+end|code-block|syntax|javascript|1499631|然后，您可以使用任何与===一起工作的东西，这有时很不错。或者这样做：|1499632|not_valid+=+nil,+0
case+val1+with+*not_valid
++++++#+do+stuff
+end
+#do+other+stuff
+case+val2+with+*not_valid,+false++++#Test+for+values+that+is+nil,+0+or+false
++++++#+do+other+other+stuff
+end|1499633|这并不是很好的OOP，但它非常灵活，而且很有效。无论如何，我的ifs通常以cases结尾。|1499634|当然，Enum.any?/Enum.include?也可以工作……如果你想变得更加神秘：|1499635|if+[0,+nil].include?+val
++++#do+stuff
end|1499636|正确的做法当然是定义一个方法或函数。或者，如果您必须对多个值执行相同的操作，可以组合使用这些很好的迭代器。|1499637|entityMap^0|B|4|0|0|B|3|0|0|V|2|11|4|0|3|9|D|D|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|16|8|@$9|17|A|18|B|C]|$9|19|A|1A|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|6|7|1B|8|@$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]]|D|@]|E|$]]|$1|S|3|T|5|H|7|1G|8|@]|D|@]|E|$I|J]]|$1|U|3|V|5|6|7|1H|8|@]|D|@]|E|$]]|$1|W|3|-4|5|6|7|1I|8|@]|D|@]|E|$]]]|X|$]]

You can use <code>case</code> if you like:

<pre><code> case val with nil, 0
 # do stuff
 end
</code></pre>

Then you can use anything that works with <code>===</code>, which is nice sometimes. Or do something like this:

<pre><code>not_valid = nil, 0
case val1 with *not_valid
 # do stuff
 end
 #do other stuff
 case val2 with *not_valid, false #Test for values that is nil, 0 or false
 # do other other stuff
 end
</code></pre>

It's not exactly good OOP, but it's very flexible and it works. My <code>if</code>s usually end up as <code>case</code>s anyway.

Of course <code>Enum.any?</code>/<code>Enum.include?</code> kind of works too ... if you like to get really cryptic:

<pre><code>if [0, nil].include? val
 #do stuff
end
</code></pre>

The right thing to do is of course to define a method or function. Or, if you have to do the same thing with many values, use a combination of those nice iterators.

blocks|key|1714818|text|我真的很喜欢Rails的blank?方法，但是它不会为0返回true。所以你可以添加你的方法：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1714819|def+nil_zero?+
++if+respond_to?(:zero?)+
++++zero?+
++else+
++++!self+
++end+
end+|code-block|syntax|javascript|1714820|它将检查某个值是否为nil或0：|1714821|nil.nil_zero?
=>+true
0.nil_zero?
=>+true
10.nil_zero?
=>+false

if+val.nil_zero?
++#...
end|1714822|entityMap^0|C|6|R|1|U|4|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|P|$]]

I really like Rails <code>blank?</code> method for that kind of things, but it won't return <code>true</code> for <code>0</code>. So you can add your method:

<pre><code>def nil_zero? 
 if respond_to?(:zero?) 
 zero? 
 else 
 !self 
 end 
end 
</code></pre>

And it will check if some value is nil or 0:

<pre><code>nil.nil_zero?
=&gt; true
0.nil_zero?
=&gt; true
10.nil_zero?
=&gt; false

if val.nil_zero?
 #...
end
</code></pre>

blocks|key|1499819|text|而不是猴子修补一个类，you+could+use+refinements从Ruby2.1开始。改进类似于猴子修补；因为它们允许您修改类，但修改仅限于您希望在其中使用它的范围。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1499820|如果你想做一次检查，这就有点过分了，但如果你想重复一次，这是一个很好的替代方法。|1499821|module+NilOrZero
++refine+Object+do
++++def+nil_or_zero?
++++++nil?+or+zero?
++++end
++end
end

using+NilOrZero
class+Car
++def+initialize(speed:+100)
++++puts+speed.nil_or_zero?
++end
end

car+=+Car.new++++++++++++++#+false
car+=+Car.new(speed:+nil)++#+true
car+=+Car.new(speed:+0)++++#+true|code-block|syntax|javascript|1499822|最近一分钟内要将范围限定到文件的Refinements+were+changed。因此，前面的例子可能已经说明了这一点，这是不会起作用的。|1499823|class+Car
++using+NilOrZero
end|1499824|entityMap|0|LINK|mutability|MUTABLE|url|http://www.ruby-doc.org/core-2.1.2/doc/syntax/refinements_rdoc.html|1|https://www.ruby-forum.com/topic/4409740^0|B|P|0|0|0|0|G|O|1|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|6|7|12|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|13|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|14|8|@]|9|@$A|15|B|16|1|17]]|C|$]]|$1|M|3|N|5|H|7|18|8|@]|9|@]|C|$I|J]]|$1|O|3|-4|5|6|7|19|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]|W|$5|R|S|T|C|$U|X]]]]

Instead of monkey patching a class, <a href="http://www.ruby-doc.org/core-2.1.2/doc/syntax/refinements_rdoc.html" rel="nofollow">you could use refinements</a> starting in Ruby 2.1. Refinements are similar to monkey patching; in that, they allow you to modify the class, but the modification is limited to the scope you wish to use it in.

This is overkill if you want to do this check once, but if you are repeating yourself it's a great alternative to monkey patching.

<pre><code>module NilOrZero
 refine Object do
 def nil_or_zero?
 nil? or zero?
 end
 end
end

using NilOrZero
class Car
 def initialize(speed: 100)
 puts speed.nil_or_zero?
 end
end

car = Car.new # false
car = Car.new(speed: nil) # true
car = Car.new(speed: 0) # true
</code></pre>

<a href="https://www.ruby-forum.com/topic/4409740" rel="nofollow">Refinements were changed</a> in the last minute to be scoped to the file. So earlier examples may have shown this, which will not work.

<pre><code>class Car
 using NilOrZero
end
</code></pre>

blocks|key|1715076|text|对于nil和0，其计算结果为true：nil.to_s.to_d+==+0|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1715077|entityMap^0|J|I|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

This evaluates to true for nil and zero: <code>nil.to_s.to_d == 0</code>

blocks|key|1715139|text|unless+(val+%7C%7C+0).zero?

++++#+do+stufff

end|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1715140|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>unless (val || 0).zero?

 # do stufff

end
</code></pre>

blocks|key|1715204|text|在单个伸展中，您可以执行以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1715205|[do_something]+if+val.to_i+==+0|code-block|syntax|javascript|1715206|nil.to_i将返回0|offset|length|style|CODE|1715207|entityMap^0|0|0|0|8|B|1|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]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

In a single stretch you can do this:
<pre><code>[do_something] if val.to_i == 0
</code></pre>
<code>nil.to_i</code> will return <code>0</code>

blocks|key|1714706|text|另一种解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1714707|if+val.to_i+==+0
++#+do+stuff
end|code-block|syntax|javascript|1714708|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|$]]

Another solution:

<pre><code>if val.to_i == 0
 # do stuff
end
</code></pre>

blocks|key|1714612|text|val+%7C%7C=+0
if+val+==+0
#+do+something+here
end|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1714613|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>val ||= 0
if val == 0
# do something here
end
</code></pre>

I am looking for a concise way to check a value to see if it is nil or zero. Currently I am doing something like:

<pre><code>if (!val || val == 0)
 # Is nil or zero
end
</code></pre>

But this seems very clumsy.

Best ruby idiom for "nil or zero"

我正在寻找一种简明的方法来检查一个值，看看它是零还是零。目前我正在做类似这样的事情：if (!val || val == 0)  # Is nil or zeroend但这似乎非常笨拙。

问"nil or zero“的最佳ruby成语
EN

回答 17

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问"nil or zero“的最佳ruby成语EN

回答 17

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