blocks|key|834639|text|您可以使用is_a?方法|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|834640|>>+1.is_a?+Integer
=>+true
>>+"dadadad@asdasd.net".is_a?+Integer
=>+false
>>+nil.is_a?+Integer
=>+false|code-block|syntax|javascript|834641|entityMap^0|5|5|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

You can use the <code>is_a?</code> method

<pre><code>&gt;&gt; 1.is_a? Integer
=&gt; true
&gt;&gt; "dadadad@asdasd.net".is_a? Integer
=&gt; false
&gt;&gt; nil.is_a? Integer
=&gt; false
</code></pre>

blocks|key|834559|text|对字符串使用正则表达式：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|834560|def+is_numeric?(obj)+
+++obj.to_s.match(/\A[%2B-]?\d%2B?(\.\d%2B)?\Z/)+==+nil+?+false+:+true
end|code-block|syntax|javascript|834561|如果想要检查变量是否为某种类型，可以简单地使用kind_of?|offset|length|style|CODE|834562|1.kind_of?+Integer+#true
(1.5).kind_of?+Float+#true
is_numeric?+"545"++#true
is_numeric?+"2aa"++#false|834563|entityMap^0|0|0|N|8|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

Use a regular expression on a string:

<pre><code>def is_numeric?(obj) 
 obj.to_s.match(/\A[+-]?\d+?(\.\d+)?\Z/) == nil ? false : true
end
</code></pre>

If you want to check if a variable is of certain type, you can simply use <code>kind_of?</code>:

<pre><code>1.kind_of? Integer #true
(1.5).kind_of? Float #true
is_numeric? "545" #true
is_numeric? "2aa" #false
</code></pre>

blocks|key|1049465|text|如果您不确定变量的类型(它可以是数字字符的字符串)，假设它是传递给params的信用卡号码，那么它最初将是一个字符串，但您希望确保其中不包含任何字母字符，我将使用以下方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1049466|++++def+is_number?(obj)
++++++++obj.to_s+==+obj.to_i.to_s
++++end

++++is_number?+"123fh"+#+false
++++is_number?+"12345"+#+true|code-block|syntax|javascript|1049467|@Benny指出了这种方法的疏忽，请记住这一点：|1049468|is_number?+"01"+#+false.+oops!|1049469|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're uncertain of the type of the variable (it could be a string of number characters), say it was a credit card number passed into the params, so it would originally be a string but you want to make sure it doesn't have any letter characters in it, I would use this method:

<pre><code> def is_number?(obj)
 obj.to_s == obj.to_i.to_s
 end

 is_number? "123fh" # false
 is_number? "12345" # true
</code></pre>

@Benny points out an oversight of this method, keep this in mind:

<pre><code>is_number? "01" # false. oops!
</code></pre>

blocks|key|834617|text|这里有var.is_a?+Class+(在您的例子中是：var.is_a?+Integer)；这可能符合要求。或者是Integer(var)，如果它不能解析它就会抛出一个异常。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|834618|entityMap^0|3|F|S|H|1M|C|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

There's <code>var.is_a? Class</code> (in your case: <code>var.is_a? Integer</code>); that might fit the bill. Or there's <code>Integer(var)</code>, where it'll throw an exception if it can't parse it.

blocks|key|1049599|text|你可以使用三重相等。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1049600|if+Integer+===+21+
++++puts+"21+is+Integer"
end|code-block|syntax|javascript|1049601|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|$]]

You can use triple equal.

<pre><code>if Integer === 21 
 puts "21 is Integer"
end
</code></pre>

blocks|key|1049406|text|一种更“鸭子类型”的方式是使用respond_to?，这样也可以使用“类似整数”或“类似字符串”的类|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1049407|if(s.respond_to?(:match)+&&+s.match(".com")){
++puts+"It's+a+.com"
else
++puts+"It's+not"
end|code-block|syntax|javascript|1049408|entityMap^0|F|B|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

A more "duck typing" way is to use <code>respond_to?</code> this way "integer-like" or "string-like" classes can also be used

<pre><code>if(s.respond_to?(:match) &amp;&amp; s.match(".com")){
 puts "It's a .com"
else
 puts "It's not"
end
</code></pre>

blocks|key|834938|text|如果不需要转换零值，我发现to_i和to_f方法非常有用，因为它们会将字符串转换为零值(如果不能转换或为零)或实际的Integer或Float值。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|834939|"0014.56".to_i+#+=>+14
"0014.56".to_f+#+=>+14.56
"0.0".to_f+#+=>+0.0
"not_an_int".to_f+#+0
"not_a_float".to_f+#+0.0

"0014.56".to_f+?+"I'm+a+float"+:+"I'm+not+a+float+or+the+0.0+float"+
#+=>+I'm+a+float
"not+a+float"+?+"I'm+a+float"+:+"I'm+not+a+float+or+the+0.0+float"+
#+=>+"I'm+not+a+float+or+the+0.0+float"|code-block|syntax|javascript|834940|EDIT2+:小心，0整数值不是假的，它是真的(!!0+#=>+true)+(谢谢@EDIT2)|834941|编辑|834942|我刚发现暗箱的事...似乎只有当数字排在第一位时才会发生|834943|"12blah".to_i+=>+12|834944|entityMap^0|D|4|I|4|1M|7|1U|5|0|0|A|1|O|C|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|14|8|@$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|19|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|1A|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1B|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|1C|8|@]|D|@]|E|$]]]|T|$]]

In case you don't need to convert zero values, I find the methods <code>to_i</code> and <code>to_f</code> to be extremely useful since they will convert the string to either a zero value (if not convertible or zero) or the actual <code>Integer</code> or <code>Float</code> value.

<pre><code>"0014.56".to_i # =&gt; 14
"0014.56".to_f # =&gt; 14.56
"0.0".to_f # =&gt; 0.0
"not_an_int".to_f # 0
"not_a_float".to_f # 0.0

"0014.56".to_f ? "I'm a float" : "I'm not a float or the 0.0 float" 
# =&gt; I'm a float
"not a float" ? "I'm a float" : "I'm not a float or the 0.0 float" 
# =&gt; "I'm not a float or the 0.0 float"
</code></pre>

EDIT2 : be careful, the <code>0</code> integer value is not falsey it's truthy (<code>!!0 #=&gt; true</code>) (thanks @prettycoder)

EDIT

Ah just found out about the dark cases... seems to only happen if the number is in first position though

<pre><code>"12blah".to_i =&gt; 12
</code></pre>

blocks|key|1049633|text|使用refinements充分利用the+answer+of+Alex+D|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1049634|module+CoreExtensions
++module+Integerable
++++refine+String+do
++++++def+integer?
++++++++Integer(self)
++++++rescue+ArgumentError
++++++++false
++++++else
++++++++true
++++++end
++++end
++end
end|code-block|syntax|javascript|1049635|稍后，在你的课堂上：|1049636|require+'core_ext/string/integerable'

class+MyClass
++using+CoreExtensions::Integerable

++def+method
++++'my_string'.integer?
++end
end|1049637|entityMap|0|LINK|mutability|MUTABLE|url|http://ruby-doc.org/core-2.3.1/doc/syntax/refinements_rdoc.html|1|https://stackoverflow.com/questions/4589968/checking-if-a-variable-is-an-integer#answer-18114479^0|2|B|0|H|K|1|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]|$A|10|B|11|1|12]]|C|$]]|$1|D|3|E|5|F|7|13|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|14|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|15|8|@]|9|@]|C|$G|H]]|$1|M|3|-4|5|6|7|16|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]|U|$5|P|Q|R|C|$S|V]]]]

To capitalize on <a href="https://stackoverflow.com/questions/4589968/checking-if-a-variable-is-an-integer#answer-18114479">the answer of Alex D</a>, using <a href="http://ruby-doc.org/core-2.3.1/doc/syntax/refinements_rdoc.html" rel="nofollow noreferrer">refinements</a>:

<pre><code>module CoreExtensions
 module Integerable
 refine String do
 def integer?
 Integer(self)
 rescue ArgumentError
 false
 else
 true
 end
 end
 end
end
</code></pre>

Later, in you class:

<pre><code>require 'core_ext/string/integerable'

class MyClass
 using CoreExtensions::Integerable

 def method
 'my_string'.integer?
 end
end
</code></pre>

blocks|key|1049552|text|在尝试确定某个东西是字符串还是任何类型的数字之前，我也遇到过类似的问题。我尝试过使用正则表达式，但这对于我的用例来说并不可靠。相反，您可以检查变量的类，以查看它是否是Numeric类的后代。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1049553|if+column.class+<+Numeric
++number_to_currency(column)
else
++column.html_safe
end|code-block|syntax|javascript|1049554|在这种情况下，您还可以替换任何数值子代:+BigDecimal、Date::Infinity、Integer、Fixnum、Float、Bignum、Rational、Complex|1049555|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|$]]

I have had a similar issue before trying to determine if something is a string or any sort of number whatsoever. I have tried using a regular expression, but that is not reliable for my use case. Instead, you can check the variable's class to see if it is a descendant of the Numeric class.

<pre><code>if column.class &lt; Numeric
 number_to_currency(column)
else
 column.html_safe
end
</code></pre>

In this situation, you could also substitute for any of the Numeric descendants: BigDecimal, Date::Infinity, Integer, Fixnum, Float, Bignum, Rational, Complex

Does Rails 3 or Ruby have a built-in way to check if a variable is an integer?

For example,

<pre><code>1.is_an_int #=&gt; true
"dadadad@asdasd.net".is_an_int #=&gt; false?
</code></pre>

Checking if a variable is an integer

Rails 3或Ruby有内置的方法来检查变量是否为整数吗？例如,1.is_an_int #=> true"dadadad@asdasd.net".is_an_int #=> false?

问检查变量是否为整数
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回答 9

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