Difference - unless / if

Question

Can anyone explain me the difference between if and unless and when to use it?

Answer 1

unless is just a negated if. That is, it executes whatever it contains if the condition is not true.

unless foo?
    # blabla
end

Simply means

if !foo?
    # blabla
end

It's all a matter of what you find easier to read, really.

See also: Unless, The Abused Ruby Conditional