Ruby retry incorrect user input

I need to retry incorrect user input but my piece of code doesn't work

def parse_param
begin 
  option = gets.chomp
  option = option.to_i
rescue 
  retry if option > 6
end

What am I doing wrong here?

> What am I doing wrong here?

The rescue section will only be entered if an exception occurs in the begin block (see the docs for Exception Handling).

Since you don't raise any exception yourself and the remaining code doesn't raise one either, the rescue section is not executed.

You could manually raise an exception this way: (just for demonstation purposes)

def parse_param
  begin 
    option = gets.chomp
    option = option.to_i
    raise if option > 6
    option
  rescue 
    retry
  end
end

However, raising an exception just to rescue it right-away is overly complicated. Also, an exception should be used for exceptional situations, i.e. something unexpected that your code cannot properly handle and which should be escalated to the caller.

For normal control flow, you could instead use a simple loop along with break, e.g.:

def parse_param
  loop do
    option = gets.chomp.to_i
    break option unless option > 6
  end
end

Ruby also has a redo statement which can be used to re-run the current iteration: (although it's rarely seen)

def parse_param
  loop do
    option = gets.chomp.to_i
    redo if option > 6
    break option
  end
end

The answer of Stefan already explains why your current solution does not work. I just wanted to add an additional option.

Instead of doing a loop with loop, you could use while or until.

def parse_param
  option = gets.chomp.to_i while !option || option > 6
  option
end

Note that we need !option as an additional check, since the initial value of option is nil on the first check.