Automatic counter in Ruby for each?
RubySyntaxRuby Problem Overview
I want to use a for-each and a counter:
i=0
for blah in blahs
puts i.to_s + " " + blah
i+=1
end
Is there a better way to do it?
Note: I don't know if blahs
is an array or a hash, but having to do blahs[i]
wouldn't make it much sexier. Also I'd like to know how to write i++
in Ruby.
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).
Should've used puts "#{i} #{blah}"
which is a lot more succinct.
Ruby Solutions
Solution 1 - Ruby
As people have said, you can use
each_with_index
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:
blahs.each_with_index.map { |blah, index| something(blah, index)}
blahs.map.with_index { |blah, index| something(blah, index) }
This is something you can do from ruby 1.8.7 and 1.9.
Solution 2 - Ruby
[:a, :b, :c].each_with_index do |item, i|
puts "index: #{i}, item: #{item}"
end
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.
Solution 3 - Ruby
Yes, it's collection.each
to do loops, and then each_with_index
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: http://poignantguide.net/ruby/).
Taken from the Ruby source code:
hash = Hash.new
%w(cat dog wombat).each_with_index {|item, index|
hash[item] = index
}
hash #=> {"cat"=>0, "wombat"=>2, "dog"=>1}
Solution 4 - Ruby
If you don't have the new version of each_with_index
, you can use the [zip
](http://ruby-doc.org/core/classes/Enumerable.html#M003138 "Enumerable#zip") method to pair indexes with elements:
blahs = %w{one two three four five}
puts (1..blahs.length).zip(blahs).map{|pair|'%s %s' % pair}
which produces:
1 one
2 two
3 three
4 four
5 five
Solution 5 - Ruby
As to your question about doing i++
, well, you cannot do that in Ruby. The i += 1
statement you had is exactly how you're supposed to do it.
Solution 6 - Ruby
The [enumerating enumerable][1] series is pretty nice.
[1]: http://www.globalnerdy.com/tag/enumerable/ "enumerating enumerable"
Solution 7 - Ruby
If you want to get index of ruby for each, then you can use
.each_with_index
Here is an example to show how .each_with_index
works:
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
This will print:
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
Solution 8 - Ruby
If blahs
is a class that mixes in Enumerable, you should be able to do this:
blahs.each_with_index do |blah, i|
puts("#{i} #{blah}")
end