Checking if a variable is not nil and not zero in ruby

unless discount.nil? || discount == 0
  # ...
end

class Object
  def nil_zero?
    self.nil? || self == 0
  end
end

# which lets you do
nil.nil_zero? # returns true
0.nil_zero?   # returns true
1.nil_zero?   # returns false
"a".nil_zero? # returns false

unless discount.nil_zero?
  # do stuff...
end

Beware of the usual disclaimers... great power/responsibility, monkey patching leading to the dark side etc.

ok, after 5 years have passed....

if discount.try :nonzero?
  ...
end

It's important to note that try is defined in the ActiveSupport gem, so it is not available in plain ruby.

unless [nil, 0].include?(discount) 
  # ...
end

You could do this:

if (!discount.nil? && !discount.zero?)

The order is important here, because if discount is nil, then it will not have a zero? method. Ruby's short-circuit evaluation should prevent it from trying to evaluate discount.zero?, however, if discount is nil.

if (discount||0) != 0
  #...
end

I prefer using a more cleaner approach :

val.to_i.zero?

val.to_i will return a 0 if val is a nil,

after that, all we need to do is check whether the final value is a zero.

Yes, we do have a clean way in ruby.

discount.to_f.zero?

This check handles good amount of cases i.e. discount may be nil, discount may be int 0, discount may be float 0.0, discount may be string "0.0", "0".

You could initialize discount to 0 as long as your code is guaranteed not to try and use it before it is initialized. That would remove one check I suppose, I can't think of anything else.

Alternative solution is to use Refinements, like so:

module Nothingness
  refine Numeric do
    alias_method :nothing?, :zero?
  end

  refine NilClass do
    alias_method :nothing?, :nil?
  end
end

using Nothingness

if discount.nothing?
  # do something
end

I believe the following is good enough for ruby code. I don't think I could write a unit test that shows any difference between this and the original.

if discount != 0
end