Ruby check if nil before calling method

Question

I have a string in Ruby on which I\'m calling the strip method to remove the leading and trailing whitespace. e.g.

s = \"12345 \"
s.strip

H

Answer 1

Method which works for me (I know, I should never pollute pristine Object space, but it's so convenient that I will take a risk):

class Object
  def unless_nil(default = nil, &block)
    nil? ? default : block[self]
  end
end

p "123".unless_nil(&:length) #=> 3
p nil.unless_nil("-", &:length) #=> "-"

In your particular case it could be:

data[2][1][6].unless_nil { |x| x.split(":")[1].unless_nil(&:strip) }

Answer 2

To complete the options shown here, there is the "Existence Check Shorthand", recommended in the Ruby Style Guide:

Use &&= to preprocess variables that may or may not exist. Using &&= will change the value only if it exists [means, is not nil], removing the need to check its existence with if.

So in your case you would do:

s = "12345 "
s &&= s.strip

Answer 3

Ruby 2.3.0 added a safe navigation operator (&.) that checks for nil before calling a method.

s&.strip

If s is nil, this expressions returns nil instead of raising NoMethodError.

Answer 4

You could simply do this

s.try(:strip)

Answer 5

ActiveSupport comes with a method for that : try. For example, an_object.try :strip will return nil if an_object is nil, but will proceed otherwise. The syntax is the same as send. Cf active_support_core_extensions.html#try.