blocks|key|350605|text|是的，先用collection.each来做循环，然后用each_with_index来获取索引。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|350606|你可能应该读一本Ruby的书，因为这是Ruby的基础，如果你不知道它，你会有大麻烦的(试试：http://poignantguide.net/ruby/)。|350607|取自Ruby源代码：|350608|+hash+=+Hash.new
+%25w(cat+dog+wombat).each_with_index+{%7Citem,+index%7C
+++hash[item]+=+index
+}
+hash+++#=>+{"cat"=>0,+"wombat"=>2,+"dog"=>1}|code-block|syntax|javascript|350609|entityMap|0|LINK|mutability|MUTABLE|url|http://poignantguide.net/ruby/^0|5|F|S|F|0|1A|U|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|11|8|@]|D|@$9|12|A|13|1|14]]|E|$]]|$1|H|3|I|5|6|7|15|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|16|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

Yes, it's <code>collection.each</code> to do loops, and then <code>each_with_index</code> to get the index. 

You probably ought to read a Ruby book because this is fundamental Ruby and if you don't know it, you're going to be in big trouble (try: <a href="http://poignantguide.net/ruby/" rel="nofollow noreferrer">http://poignantguide.net/ruby/</a>).

Taken from the Ruby source code:

<pre><code> hash = Hash.new
 %w(cat dog wombat).each_with_index {|item, index|
 hash[item] = index
 }
 hash #=&gt; {"cat"=&gt;0, "wombat"=&gt;2, "dog"=&gt;1}
</code></pre>

blocks|key|3341979|text|[:a,+:b,+:c].each_with_index+do+%7Citem,+i%7C
++puts+"index:+#{i},+item:+#{item}"
end|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|3341980|你不能用for做这件事。无论如何，我通常喜欢对每个人进行更具声明性的调用。部分原因是当您达到for语法的限制时，它很容易转换为其他形式。|unstyled|3341981|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>[:a, :b, :c].each_with_index do |item, i|
 puts "index: #{i}, item: #{item}"
end
</code></pre>

You can't do this with for. I usually like the more declarative call to each personally anyway. Partly because its easy to transition to other forms when you hits the limit of the for syntax.

blocks|key|3341988|text|如果blahs是一个混合了Enumerable的类，你应该能够这样做：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3341989|blahs.each_with_index+do+%7Cblah,+i%7C
++puts("#{i}+#{blah}")
end|code-block|syntax|javascript|3341990|entityMap^0|2|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|$]]

If <code>blahs</code> is a class that mixes in Enumerable, you should be able to do this:

<pre><code>blahs.each_with_index do |blah, i|
 puts("#{i} #{blah}")
end
</code></pre>

blocks|key|348250|text|正如人们所说，您可以使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|348251|each_with_index|code-block|syntax|javascript|348252|但是，如果您希望使用不同于"each“的迭代器的索引(例如，如果您希望映射到索引或类似的东西)，您可以使用each_with_index方法连接枚举器，或者简单地使用with_index：|348253|blahs.each_with_index.map+{+%7Cblah,+index%7C+something(blah,+index)}

blahs.map.with_index+{+%7Cblah,+index%7C+something(blah,+index)+}|348254|这是你可以在ruby+1.8.7和1.9中做的事情。|348255|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|$]]

As people have said, you can use 

<pre><code>each_with_index
</code></pre>

but if you want indices with an iterator different to "each" (for example, if you want to map with an index or something like that) you can concatenate enumerators with the each_with_index method, or simply use with_index:

<pre><code>blahs.each_with_index.map { |blah, index| something(blah, index)}

blahs.map.with_index { |blah, index| something(blah, index) }
</code></pre>

This is something you can do from ruby 1.8.7 and 1.9.

blocks|key|350629|text|enumerating+enumerable系列相当不错。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|350630|entityMap|0|LINK|mutability|MUTABLE|url|http://www.globalnerdy.com/tag/enumerable/^0|0|M|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

The <a href="http://www.globalnerdy.com/tag/enumerable/" rel="nofollow noreferrer" title="enumerating enumerable">enumerating enumerable</a> series is pretty nice.

blocks|key|3342037|text|至于你关于做i%2B%2B的问题，嗯，你不能在Ruby语言中做到这一点。您拥有的i+%2B=+1语句就是您应该执行的操作。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3342038|entityMap^0|6|3|10|6|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

As to your question about doing <code>i++</code>, well, you cannot do that in Ruby. The <code>i += 1</code> statement you had is exactly how you're supposed to do it.

blocks|key|353321|text|如果没有新版本的each_with_index，可以使用zip方法将索引与元素配对：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|353322|blahs+=+%25w{one+two+three+four+five}
puts+(1..blahs.length).zip(blahs).map{%7Cpair%7C'%25s+%25s'+%25+pair}|code-block|syntax|javascript|353323|这会产生：|353324|1+one
2+two
3+three
4+four
5+five|353325|entityMap|0|LINK|mutability|MUTABLE|url|http://ruby-doc.org/core/classes/Enumerable.html#M003138^0|8|F|S|3|S|3|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]]|D|@$9|11|A|12|1|13]]|E|$]]|$1|F|3|G|5|H|7|14|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|15|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|16|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

If you don't have the new version of <code>each_with_index</code>, you can use the <a href="http://ruby-doc.org/core/classes/Enumerable.html#M003138" rel="noreferrer" title="Enumerable#zip"><code>zip</code></a> method to pair indexes with elements:

<pre><code>blahs = %w{one two three four five}
puts (1..blahs.length).zip(blahs).map{|pair|'%s %s' % pair}
</code></pre>

which produces:

<pre><code>1 one
2 two
3 three
4 four
5 five
</code></pre>

blocks|key|350653|text|如果你想得到每个的ruby索引，那么你可以使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|350654|.each_with_index|code-block|syntax|javascript|350655|下面的示例展示了.each_with_index的工作原理：|offset|length|style|CODE|350656|range+=+('a'..'z').to_a
length+=+range.length+-+1
range.each_with_index+do+%7Cletter,+index%7C
++++print+letter+%2B+"+"
++++if+index+==+length
++++++++puts+"You+are+at+last+item"
++++end
end|350657|这将打印以下内容：|350658|a+b+c+d+e+f+g+h+i+j+k+l+m+n+o+p+q+r+s+t+u+v+w+x+y+z+You+are+at+last+item|350659|entityMap^0|0|0|8|G|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

If you want to get index of ruby for each, then you can use

<pre><code>.each_with_index
</code></pre>

Here is an example to show how <code>.each_with_index</code> works:

<pre><code>range = ('a'..'z').to_a
length = range.length - 1
range.each_with_index do |letter, index|
 print letter + " "
 if index == length
 puts "You are at last item"
 end
end
</code></pre>

This will print:

<pre><code>a b c d e f g h i j k l m n o p q r s t u v w x y z You are at last item
</code></pre>

I want to use a for-each and a counter:

<pre><code>i=0
for blah in blahs
 puts i.to_s + " " + blah
 i+=1
end
</code></pre>

Is there a better way to do it?

Note: I don't know if <code>blahs</code> is an array or a hash, but having to do <code>blahs[i]</code> wouldn't make it much sexier. Also I'd like to know how to write <code>i++</code> in Ruby.

<hr>

Technically, Matt's and Squeegy's answer came in first, but I'm giving best answer to paradoja so spread around the points a bit on SO. Also his answer had the note about versions, which is still relevant (as long as my Ubuntu 8.04 is using Ruby 1.8.6).

<hr>

Should've used <code>puts "#{i} #{blah}"</code> which is a lot more succinct.

Automatic counter in Ruby for each?

Ruby语言

Ubuntu

我想使用一个for-each和一个计数器：i=0for blah in blahs    puts i.to_s + " " + blah    i+=1end有没有更好的方法呢？注：我不知道blahs是一个数组还是一个哈希，但是必须做blahs[i]并不会让它更有吸引力。另外，我想知道如何用Ruby语言编写i++。从...

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