blocks|key|318783|text|ending+=+string.reverse[0...n].reverse|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|318784|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>ending = string.reverse[0...n].reverse
</code></pre>

blocks|key|3064807|text|嗯，我能想到的最简单的解决方法是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3064808|ending+=+str[-n..-1]+%7C%7C+str|code-block|syntax|javascript|3064809|(编辑：or运算符的优先级低于赋值，因此请确保使用%7C%7C。)|offset|length|style|CODE|3064810|entityMap^0|0|0|4|2|P|2|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|$]]

Well, the easiest workaround I can think of is:

<pre><code>ending = str[-n..-1] || str
</code></pre>

(EDIT: The <code>or</code> operator has lower precedence than assignment, so be sure to use <code>||</code> instead.)

blocks|key|318812|text|您尝试过正则表达式吗？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|318813|string.match(/(.{0,#{n}}$)/)
ending=$1|code-block|syntax|javascript|318814|正则表达式在字符串的末尾捕获尽可能多的字符，但不超过n，并将其存储在$1中。|318815|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|$]]

Have you tried a regex?

<pre><code>string.match(/(.{0,#{n}}$)/)
ending=$1
</code></pre>

The regex captures as many characters it can at the end of the string, but no more than n. And stores it in $1.

blocks|key|3277856|text|这里你有一个一行，你可以放一个大于字符串大小的数字：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3277857|"123".split(//).last(5).to_s|code-block|syntax|javascript|3277858|对于ruby+1.9%2B|3277859|"123".split(//).last(5).join("").to_s|3277860|对于拼音2.0%2B，join返回一个字符串|3277861|"123".split(//).last(5).join|3277862|entityMap^0|0|0|0|0|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]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

Here you have a one liner, you can put a number greater than the size of the string:

<pre><code>"123".split(//).last(5).to_s
</code></pre>

For ruby 1.9+

<pre><code>"123".split(//).last(5).join("").to_s
</code></pre>

For ruby 2.0+, join returns a string

<pre><code>"123".split(//).last(5).join
</code></pre>

blocks|key|3277911|text|要从字符串中获取最后n个字符，可以这样做|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3277912|a-n，n，如果a是数组。|3277913|如果你想要一个，这里有一个例子。|3277914|ruby-1.9.2-p180+:006+>a=+"911234567890“|3277915|=>+"911234567890“|3277916|ruby-1.9.2-p180+:009+>+a-5,5|3277917|=>+"67890“|3277918|ruby-1.9.2-p180+:010+>+a-7,7|3277919|=>+"4567890“|3277920|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|U|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|V|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|W|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|X|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|Y|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|Z|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|10|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|11|8|@]|9|@]|A|$]]|$1|R|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|S|$]]

To get the last n characters from a string, you could do this 

a[-n, n] if a is the array.

Here's and example if you would want one.

ruby-1.9.2-p180 :006 > a = "911234567890"

=> "911234567890"

ruby-1.9.2-p180 :009 > a[-5,5]

=> "67890" 

ruby-1.9.2-p180 :010 > a[-7,7]

=> "4567890"

blocks|key|320756|text|改进了EmFi的答案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|320757|string[/.{,#{n}}\z/m]|code-block|syntax|javascript|320758|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|$]]

Improvement on EmFi's answer.

<pre><code>string[/.{,#{n}}\z/m]
</code></pre>

blocks|key|318861|text|在纯Ruby+(没有Rails)中，您可以这样做|type|unstyled|depth|inlineStyleRanges|entityRanges|data|318862|string.chars.last(n).join|code-block|syntax|javascript|318863|例如：|318864|2.4.1+:009+>+a+=+'abcdefghij'
+=>+"abcdefghij"
2.4.1+:010+>+a.chars.last(5).join
+=>+"fghij"
2.4.1+:011+>+a.chars.last(100).join
+=>+"abcdefghij"|318865|如果您使用的是Ruby+on+Rails，则可以在string对象上调用first和last方法。这些方法是首选的，因为它们简洁直观。|offset|length|style|CODE|318866|318867|[1]+pry(main)>+a+=+'abcdefg'++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+=>+"abcdefg"
[2]+pry(main)>+a.first(3)+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+=>+"abc"
[3]+pry(main)>+a.last(4)++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+=>+"defg"|318868|entityMap^0|0|0|0|0|10|5|16|4|0|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|W|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|X|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Z|8|@$M|10|N|11|O|P]|$M|12|N|13|O|P]]|9|@]|A|$]]|$1|Q|3|H|5|6|7|14|8|@]|9|@]|A|$]]|$1|R|3|S|5|D|7|15|8|@]|9|@]|A|$E|F]]|$1|T|3|-4|5|6|7|16|8|@]|9|@]|A|$]]]|U|$]]

In straight Ruby (without Rails), you can do

<pre><code>string.chars.last(n).join
</code></pre>

For example:

<pre><code>2.4.1 :009 &gt; a = 'abcdefghij'
 =&gt; "abcdefghij"
2.4.1 :010 &gt; a.chars.last(5).join
 =&gt; "fghij"
2.4.1 :011 &gt; a.chars.last(100).join
 =&gt; "abcdefghij"
</code></pre>

If you're using Ruby on Rails, you can call methods <code>first</code> and <code>last</code> on a string object. These methods are preferred as they're succinct and intuitive.

For example:

<pre><code>[1] pry(main)&gt; a = 'abcdefg' 
 =&gt; "abcdefg"
[2] pry(main)&gt; a.first(3) 
 =&gt; "abc"
[3] pry(main)&gt; a.last(4) 
 =&gt; "defg"
</code></pre>

blocks|key|3277961|text|您可以使用以下代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3277962|string[string.length-n,string.length]|code-block|syntax|javascript|3277963|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 the following code:

<pre><code>string[string.length-n,string.length]
</code></pre>

To get the last <code>n</code> characters from a string, I assumed you could use

<pre><code>ending = string[-n..-1]
</code></pre>

but if the string is less than <code>n</code> letters long, you get <code>nil</code>.

What workarounds are available?

Background: The strings are plain ASCII, and I have access to ruby 1.9.1, and I'm using Plain Old Ruby Objects (no web frameworks).

Extracting the last n characters from a ruby string

要从字符串中获取最后一个n字符，我假设您可以使用ending = string[-n..-1]但是，如果字符串长度小于n个字母，则会得到nil。有哪些可用的解决方法？Background：字符串是纯ASCII码，我可以访问Ruby1.9.1，并且我使用的是plain Old ruby对象(没有web框架)。

问从拼音字符串中提取最后n个字符
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