blocks|key|1593266|text|也许..。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1593267|a+=+t+++++++++++++++#+=>+[1,+2,+3,+4]
a.first+a.size+-+1++#+=>+[1,+2,+3]|code-block|syntax|javascript|1593268|或|1593269|a.take+3|1593270|1593271|a.first+3|1593272|1593273|a.pop|1593274|，它将返回最后一个数组，并保留数组之前的所有内容。|1593275|或者让计算机为它的晚餐工作：|1593276|a.reverse.drop(1).reverse|1593277|1593278|class+Array
++def+clip+n=1
++++take+size+-+n
++end
end
a++++++++++#+=>+[1,+2,+3,+4]
a.clip+++++#+=>+[1,+2,+3]
a+=+a+%2B+a++#+=>+[1,+2,+3,+4,+1,+2,+3,+4]
a.clip+2+++#+=>+[1,+2,+3,+4,+1,+2]|1593279|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|12|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|13|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|14|8|@]|9|@]|A|$E|F]]|$1|K|3|H|5|6|7|15|8|@]|9|@]|A|$]]|$1|L|3|M|5|D|7|16|8|@]|9|@]|A|$E|F]]|$1|N|3|H|5|6|7|17|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|18|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|19|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1A|8|@]|9|@]|A|$]]|$1|U|3|V|5|D|7|1B|8|@]|9|@]|A|$E|F]]|$1|W|3|H|5|6|7|1C|8|@]|9|@]|A|$]]|$1|X|3|Y|5|D|7|1D|8|@]|9|@]|A|$E|F]]|$1|Z|3|-4|5|6|7|1E|8|@]|9|@]|A|$]]]|10|$]]

Perhaps...

<pre><code>a = t # =&gt; [1, 2, 3, 4]
a.first a.size - 1 # =&gt; [1, 2, 3]
</code></pre>

or

<pre><code>a.take 3
</code></pre>

or

<pre><code>a.first 3
</code></pre>

or

<pre><code>a.pop
</code></pre>

which will return the last and leave the array with everything before it

or make the computer work for its dinner:

<pre><code>a.reverse.drop(1).reverse
</code></pre>

or

<pre><code>class Array
 def clip n=1
 take size - n
 end
end
a # =&gt; [1, 2, 3, 4]
a.clip # =&gt; [1, 2, 3]
a = a + a # =&gt; [1, 2, 3, 4, 1, 2, 3, 4]
a.clip 2 # =&gt; [1, 2, 3, 4, 1, 2]
</code></pre>

blocks|key|1593591|text|出于好奇，你为什么不喜欢a[0...-1]呢？|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1593592|也许是这样的：|1593593|class+Array
++++def+drop_last
++++++++self[0...-1]
++++end
end|code-block|syntax|javascript|1593594|entityMap^0|C|9|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|S|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

Out of curiosity, why don't you like <code>a[0...-1]</code>? You want to get a slice of the array, so the slice operator seems like the idiomatic choice.

But if you need to call this all over the place, you always have the option of adding a method with a more friendly name to the Array class, like DigitalRoss suggested. Perhaps like this:

<pre><code>class Array
 def drop_last
 self[0...-1]
 end
end
</code></pre>

blocks|key|1594022|text|另一个很酷的把戏|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1594023|>>+*a,+b+=+[1,2,3]
=>+[1,+2,+3]
>>+a
=>+[1,+2]
>>+b
=>+3|code-block|syntax|javascript|1594024|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 cool trick

<pre><code>&gt;&gt; *a, b = [1,2,3]
=&gt; [1, 2, 3]
&gt;&gt; a
=&gt; [1, 2]
&gt;&gt; b
=&gt; 3
</code></pre>

blocks|key|1808706|text|如果您想对一个数组执行pop()操作(这将导致最后一项被删除)，但是您对获取数组而不是弹出的元素感兴趣，您可以使用tap(&:pop)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1808707|>+arr+=+[1,+2,+3,+4,+5]
>+arr.pop
=>+5
>+arr
=>+[1,+2,+3,+4]
>+arr.tap(&:pop)
=>+[1,+2,+3]|code-block|syntax|javascript|1808708|entityMap^0|B|5|1L|A|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

If you want to perform a <code>pop()</code> operation on an array (which is going to result in the last item deleted), but you're interested in obtaining the array instead of a popped element, you can use <code>tap(&amp;:pop)</code>:

<pre><code>&gt; arr = [1, 2, 3, 4, 5]
&gt; arr.pop
=&gt; 5
&gt; arr
=&gt; [1, 2, 3, 4]
&gt; arr.tap(&amp;:pop)
=&gt; [1, 2, 3]
</code></pre>

blocks|key|1808710|text|我是这样做的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1808711|my_array[0..-2]|code-block|syntax|javascript|1808712|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 do it like this:

<pre><code>my_array[0..-2]
</code></pre>

blocks|key|1593859|text|如何扩充drop方法本身，例如这样？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1593860|class+Array
++def+drop(n)
++++n+<+0+?+self[0...n]+:+super
++end
end|code-block|syntax|javascript|1593861|然后，您可以使用负大小从结尾处删除元素，如下所示：|1593862|[1,+2,+3,+4].drop(-1)+#=>+[1,+2,+3]
[1,+2,+3,+4].drop(-2)+#=>+[1,+2]|1593863|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|$]]

How about augmenting the drop method itself, for example like this?

<pre><code>class Array
 def drop(n)
 n &lt; 0 ? self[0...n] : super
 end
end
</code></pre>

Then you can use a negative size to remove elements from the end, like so:

<pre><code>[1, 2, 3, 4].drop(-1) #=&gt; [1, 2, 3]
[1, 2, 3, 4].drop(-2) #=&gt; [1, 2]
</code></pre>

blocks|key|1593707|text|a[0...-1]似乎是最好的方式。数组切片语法就是为此目的而创建的……|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1593708|或者，如果您不介意就地修改数组，可以只调用a.pop|1593709|>>+a+=+[1,+2,+3,+4]
>>+a.pop
>>+a
=>+[1,+2,+3]|code-block|syntax|javascript|1593710|entityMap^0|0|9|0|L|5|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|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|U|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

<code>a[0...-1]</code> seems like the best way. The array slicing syntax was created for exactly this purpose...

Alternatively, if you don't mind modifying the array in place, you could just call <code>a.pop</code>:

<pre><code>&gt;&gt; a = [1, 2, 3, 4]
&gt;&gt; a.pop
&gt;&gt; a
=&gt; [1, 2, 3]
</code></pre>

blocks|key|1594048|text|去掉一行中的最后一个元素，其余元素返回|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1594049|[1,+2,+4,+5,+6].reverse.drop(1).reverse|code-block|syntax|javascript|1594050|不过，说真的，|1594051|[1,2,3,4][0..-2]
#=>+[1,2,3]|1594052|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|$]]

To get rid of the last element in one line with the remainder returning

<pre><code>[1, 2, 4, 5, 6].reverse.drop(1).reverse
</code></pre>

Seriously though,

<pre><code>[1,2,3,4][0..-2]
#=&gt; [1,2,3]
</code></pre>

blocks|key|1593417|text|你试过"take“吗？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1593418|a.take(3)+|code-block|syntax|javascript|1593419|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|$]]

Have you tried "take"

<pre><code>a.take(3) 
</code></pre>

blocks|key|1808472|text|这将创建一个新数组，其中包含原始数组中除最后一个元素以外的所有元素：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1808473|ary2+=+ary.dup
ary2.pop|code-block|syntax|javascript|1808474|请注意，还有一些人建议使用#pop。如果你可以就地修改数组，那也没问题。如果您对此不满意，那么首先执行dup数组，如本例所示。|1808475|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|$]]

This makes a new array with all but the last elements of the original:

<pre><code>ary2 = ary.dup
ary2.pop
</code></pre>

Note that a few others have suggested using #pop. If you are ok modifying the array in place, that's fine. If you aren't ok with that, then dup the array first, as in this example.

blocks|key|1594142|text|我经常发现自己想要一个数组中除最后n个元素之外的所有元素。我已经设置了自己的函数，以一种我发现比其他解决方案更具可读性的方式来完成这项工作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1594143|class+Array
++def+all_but_the_last(n)
++++self.first(self.size+-+n)
++end
end|code-block|syntax|javascript|1594144|现在，您可以执行以下操作：|1594145|arr+=+["One",+"Two",+"Three",+"Four",+"Five"]
#+=>+["One",+"Two",+"Three",+"Four",+"Five"]

arr.all_but_the_last(1)
#+=>+["One",+"Two",+"Three",+"Four"]

arr.all_but_the_last(3)
#+=>+["One",+"Two"]

arr.all_but_the_last(5)
#+=>+[]

arr.all_but_the_last(6)
#+ArgumentError:+negative+array+size|1594146|我特意允许使用ArgumentError，以便调用者负责如何使用此方法。|1594147|entityMap^0|0|0|0|0|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]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I often find myself wanting all but the last n elements of an array. I've rigged up my own function to do this in a way that I find more readable than other solutions:

<pre><code>class Array
 def all_but_the_last(n)
 self.first(self.size - n)
 end
end
</code></pre>

Now you can do the following:

<pre><code>arr = ["One", "Two", "Three", "Four", "Five"]
# =&gt; ["One", "Two", "Three", "Four", "Five"]

arr.all_but_the_last(1)
# =&gt; ["One", "Two", "Three", "Four"]

arr.all_but_the_last(3)
# =&gt; ["One", "Two"]

arr.all_but_the_last(5)
# =&gt; []

arr.all_but_the_last(6)
# ArgumentError: negative array size
</code></pre>

I've deliberately allowed for the ArgumentError so that the caller is responsible for how they use this method. I'd love to hear comments/criticisms of this approach.

blocks|key|1808684|text|a+=+[1,2,3,4]

a[0..(a.length+-+2)]
=>+[1,2,3]|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1808685|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>a = [1,2,3,4]

a[0..(a.length - 2)]
=&gt; [1,2,3]
</code></pre>

Let's say I have a Ruby array

<pre><code>a = [1, 2, 3, 4]
</code></pre>

If I want all but the first item, I can write <code>a.drop(1)</code>, which is great. If I want all but the last item, though, I can only think of this way

<pre><code>a[0..-2] # or
a[0...-1]
</code></pre>

but neither of these seem as clean as using <code>drop</code>. Any other built-in ways I'm missing?

All but last element of Ruby array

假设我有一个Ruby数组a = [1, 2, 3, 4]如果我想要除第一项之外的所有内容，我可以编写a.drop(1)，这很棒。然而，如果我想要最后一项之外的所有东西，我只能这样想a[0..-2]   # ora[0...-1]但这两种方法似乎都不像使用drop那样干净。我还遗漏了其他内置的方法吗？

问Ruby数组中除最后一个元素外的所有元素
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回答 12

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