Question

Sometimes, you want to use an if/unless modifier but the conditionally executed part includes a local variable that is to be defined within the condition. For example,

a = [1, 2, 3]
n = 3*(x**2) + 4*x + 5 if x = a[2]
m = 6*(y**2) + 7*y + 8 unless (y = a[0]).zero?

will give a parsing error because x,y is read before the if/unless modifier. In order to avoid that, I think it is pretty much common (at least for me) to use and instead of if and or instead of unless:

x = a[2] and n = 3*(x**2) + 4*x + 5
(y = a[0]).zero? or m = 6*(y**2) + 7*y + 8

Besides the fact that it does not raise an error, is there any difference? Is there any side effects in doing this? And, is there a better way?

Answer 1

Alternatives that I would choose (and have used) when this issue arises:

if x=a[2]
  n = 3*(x**2) + 4*x + 5
end

if x=a[2] then n = 3*(x**2) + 4*x + 5 end

x=nil
n = 3*(x**2) + 4*x + 5 if x=a[2]