blocks|key|1697631|text|我认为没有比这更优雅或更具可读性的方法了。任何以某种方式将迭代与条件组合在一起的方法都只会导致黑盒代码，这意味着:条件最有可能隐藏在Array扩展中。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1697632|entityMap^0|1U|5|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|$]]

I think there is no much more elegant or readable way to write this. Any way to somehow combine an iteration with a condition will just result in blackboxed code, meaning: the condition will just most likely be hidden in an <code>Array</code> extension.

blocks|key|1911309|text|假设"process空数组“在处理后将其留空，则可以省略else：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1911310|if+array.empty?
++#+process+empty+array+
end
array.each+do+%7Cel%7C
++#+process+el
end|code-block|syntax|javascript|1911311|或者一行：|1911312|array.empty?+?+process_empty_array+:+array.each+{+%7Cel%7C+process_el+}+|1911313|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|$]]

Assuming that "process empty array" leaves it empty after processing, you can leave out the else:

<pre><code>if array.empty?
 # process empty array 
end
array.each do |el|
 # process el
end
</code></pre>

or in one line:

<pre><code>array.empty? ? process_empty_array : array.each { |el| process_el } 
</code></pre>

blocks|key|1698219|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1698220|if+(array.each+do+%7Cel%7C
++#+process+el
end).empty?
++#+process+empty+array
end|code-block|syntax|javascript|1698221|entityMap^0|0|0^^$0|@$1|2|3|-4|4|5|6|H|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|I|7|@]|8|@]|9|$D|E]]|$1|F|3|-4|4|5|6|J|7|@]|8|@]|9|$]]]|G|$]]

If <code>array</code> is empty, then it will not be iterated, so the <code>each</code> block does not need to be conditioned. Since the return value of <code>each</code> is the receiver, you can put the <code>each</code> block within the <code>empty?</code> condition.

<pre><code>if (array.each do |el|
 # process el
end).empty?
 # process empty array
end
</code></pre>

blocks|key|1911822|text|关于?|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1911823|array.each+do+%7Cx%7C
++#...
++puts+"x",x
end.empty?+and+begin
++puts+"empty!"
end|code-block|syntax|javascript|1911824|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|$]]

What about?

<pre><code>array.each do |x|
 #...
 puts "x",x
end.empty? and begin
 puts "empty!"
end
</code></pre>

blocks|key|1911930|text|我在HAML+(不是普通的Ruby)中看到的最干净的方式是这样的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1911931|-+array.each+do+%7Citem%7C
++++%25li
++++++++=+item.name
-+if+array.empty?
++++%25li.empty
++++++++Nothing+here.|code-block|syntax|javascript|1911932|正如其他答案所提到的，不需要else子句，因为它已经隐含在其他逻辑中。|offset|length|style|CODE|1911933|即使您可以在一行中执行每个-else操作，也无法实现您试图实现的标记(如果是array.empty，则为？；如果是array.present，则为<ul>？)。此外，你在问题中展示的HAML是讲述代码背后故事的最好方式，这意味着它对其他开发人员来说更具可读性和可维护性，所以我不知道你为什么要重构成更神秘的东西。|1911934|entityMap^0|0|0|E|4|0|1G|3|24|4|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|$]]|$1|M|3|N|5|6|7|V|8|@$I|W|J|X|K|L]|$I|Y|J|Z|K|L]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|P|$]]

The cleanest way I've seen this done in HAML (not plain Ruby) is something like:

<pre><code>- array.each do |item|
 %li
 = item.name
- if array.empty?
 %li.empty
 Nothing here.
</code></pre>

As mentioned by other answers, there is no need for the <code>else</code> clause because that's already implied in the other logic.

Even if you could do the each-else in one clean line, you wouldn't be able to achieve the markup you're trying to achieve (<code>&lt;p&gt;</code> if array.empty?, <code>&lt;ul&gt;</code> if array.present?). Besides, the HAML you show in your question is the best way to tell the story behind your code, which means it will be more readable and maintainable to other developers, so I don't know why you would want to refactor into something more cryptic.

blocks|key|1911960|text|我看到一些人在问如何处理这个零案例。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1911961|诀窍是将其转换为字符串。所有转换为字符串的nils都变成空字符串，所有空格继续为空。|1911962|nil.to_s.empty?
"".to_s.empty?|code-block|syntax|javascript|1911963|两者都将返回true|1911964|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|$]]

I saw some people asking how to handle this for nil cases.

The trick is to convert it to string. All nils converted to string becomes a empty string, all empty cases continue being empty.

<pre><code>nil.to_s.empty?
"".to_s.empty?
</code></pre>

both will return true

blocks|key|1698382|text|如果数组为nil，那么我们可以强制为空数组|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1698383|if+(array+%7C%7C+[]).each+do+%7Cx%7C
++#...
++puts+"x",x
end.empty?
++puts+"empty!"
end|code-block|syntax|javascript|1698384|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|$]]

An if the array is nil then we can enforce to empty array

<pre><code>if (array || []).each do |x|
 #...
 puts "x",x
end.empty?
 puts "empty!"
end
</code></pre>

1.I can't find an elegant way to write this code:

<pre><code>if array.empty?
 # process empty array
else
 array.each do |el|
 # process el
 end
end
</code></pre>

I'd like to have one loop, without writing <code>array</code> twice. I read <a href="https://groups.google.com/forum/?fromgroups#!topic/columbusrb/tzX2iAtr-_A">this</a>, but there is no solution good enough.

<hr>

2.
I am actually in an HAML template. Same question.

<pre><code>- if array.empty?
 %p No result
- else
 %ul
 - array.each do |el|
 %li el
</code></pre>

Ruby best practice : if not empty each do else in one operator

1.我找不到一种优雅的方式来编写这段代码：if array.empty?  # process empty arrayelse  array.each do |el|    # process el  endend我希望有一个循环，而不是编写两次array。我读了，但没有足够好的解决方案。我实际上是在一个HAML模板中...

问Ruby最佳实践:如果不为空，则在一个运算符中执行每个操作
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