Syntax for a for loop in ruby

0 votes
asked Jan 9, 2010 by dnb5brims

How do I do this type of for loop in Ruby?

for(int i=0; i<array.length; i++) {

}

10 Answers

0 votes
answered Jan 9, 2010 by eimantas
array.each do |element|
  element.do_stuff
end

or

for element in array do
  element.do_stuff
end

If you need index, you can use this:

array.each_with_index do |element,index|
  element.do_stuff(index)
end
0 votes
answered Jan 9, 2010 by you
['foo', 'bar', 'baz'].each_with_index {|j, i| puts "#{i} #{j}"}
0 votes
answered Jan 9, 2010 by emfi
array.each_index do |i|
  ...
end

It's not very Rubyish, but it's the best way to do the for loop from question in Ruby

0 votes
answered Jan 4, 2013 by yts

To iterate a loop a fixed number of times, try:

n.times do
  #Something to be done n times
end
0 votes
answered Jan 7, 2013 by ph0en1x
limit = array.length;
for counter in 0..limit
 --- make some actions ---
end

the other way to do that is the following

3.times do |n|
  puts n;
end

thats will print 0, 1, 2, so could be used like array iterator also

Think that variant better fit to the author's needs

0 votes
answered Jan 7, 2013 by steenslag

What? From 2010 and nobody mentioned Ruby has a fine for /in loop (it's just nobody uses it):

ar = [1,2,3,4,5,6]
for item in ar
  puts item
end
0 votes
answered Jan 16, 2013 by benjamin-crouzier

If you don't need to access your array, (just a simple for loop) you can use upto or each :

Upto:

1.9.3p392 :030 > 2.upto(4) {|i| puts i}
2
3
4
 => 2 

Each:

1.9.3p392 :031 > (2..4).each {|i| puts i}
2
3
4
 => 2..4 
0 votes
answered Jan 27, 2013 by dsz

I keep hitting this as a top link for google "ruby for loop", so I wanted to add a solution for loops where the step wasn't simply '1'. For these cases, you can use the 'step' method that exists on Numerics and Date objects. I think this is a close approximation for a 'for' loop.

start = Date.new(2013,06,30)
stop = Date.new(2011,06,30)
# step back in time over two years, one week at a time
start.step(stop, -7).each do |d| 
    puts d
end
0 votes
answered Jan 25, 2014 by believesinsanta

Ruby's enumeration loop syntax is different:

collection.each do |item|
...
end

This reads as "a call to the 'each' method of the array object instance 'collection' that takes block with 'blockargument' as argument". The block syntax in Ruby is 'do ... end' or '{ ... }' for single line statements.

The block argument '|item|' is optional but if provided, the first argument automatically represents the looped enumerated item.

0 votes
answered Sep 15, 2017 by jsh-c

The equivalence would be

for i in (0...array.size)
end

or

(0...array.size).each do |i|
end

or

i = 0
while i < array.size do
   array[i]
   i = i + 1 # where you may freely set i to any value
end
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