How do I replace a for-loop in Ruby?

Question

In Ruby it is bad style to use for-loops. This is commonly understood. A style guide recommended to me: (https://github.com/bbatsov/ruby-style-guide#source-code-layout) says: "Never use for, unless you know exactly why. Most of the time iterators should be used instead. for is implemented in terms of each (so you're adding a level of indirection), but with a twist - for doesn't introduce a new scope (unlike each) and variables defined in its block will be visible outside it." The example given is: ``` arr = [1, 2, 3] #bad for elem in arr do puts elem end # good arr.each { |elem| puts elem } ``` I have researched and I can't find an explanation as to how to simulate a for loop that provides an iterating value I can pass to places or perform arithmetic on. For example, with what would I replace: ``` for i in 0...size do puts array1[i] puts array2[size-1 - i] puts i % 2 end ``` It's easy if it's one array, but I often need the current position for other purposes. There's either a simple…

Accepted Answer

If you want to iterate over a collection and keep track of the index, use `each_with_index`:

```
fields = ["name", "age", "height"]

fields.each_with_index do |field,i|
  puts "#{i}. #{field}" # 0. name, 1. age, 2. height
end
```

Your `for i in 0...size` example becomes:

```
array1.each_with_index do |item, i|
  puts item
  puts array2[size-1 - i]
  puts i % 2
end
```

How do I replace a for-loop in Ruby?

Solution

Problem