So far we have looked at various types of loops, e.g. while loops, for loops,….etc.
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What ever type of loop you are using, there will be times when you want to one of the following:
- skip to the next iteration while part way through the current interation – this is done using the “next” keyword
- exit the loop early – this is done using the “break” keyword.
- redo the current iteration – this is done using the “redo” keyword.
We will demonstrate the next/break/redo keywords using a simple for-loop (although they can work in any type of loop)
Skipping a current loop iteration – using “next”
for i in (1..5) next if i == 3 puts i end
PS C:\Temp\irb> ruby .\nextloop.rb 1 2 4 5 PS C:\Temp\irb>
Exiting the whole loop early – using “break”
Here’s an example:
for i in (1..5) break if i == 3 puts i end
PS C:\Temp\irb> ruby .\breakloop.rb 1 2 PS C:\Temp\irb>
The break keyword has an extra feature for catching an output from a loop when the break keyword gets triggered, here’s an example of how this works:
answer = for i in (1..5) break "loop exited early" if i == 3 puts i end # outputs: 1 2 puts answer # this outputs "loop exited early"
This technique could be useful for various purposes, including capturing possible error messages and storing it into logs.
Redoing the current iteration of a loop – using “redo”
Here’s an example of the redo key-word in action:
for i in (1..5) i += 1 # I had to add this line in to avoid an infinite loop. redo if i == 3 puts i end
PS C:\Temp\irb> ruby .\redoloop.rb 2 4 4 5 6 PS C:\Temp\irb>