Coalesce (ruby method, not a SQL question)

Hi everyone,

it’s a silly question (and I’m kind of ashamed to ask it), but I frequently must do things like that:

a.present? ? a : b

``

or a real world example:

params[:user][:name].present? ? params[:user][:name] : “default name”

``

I think these are perfect cases to use a “coalesce” method. Something like:

a.coalesce(b)

params[:user][:name].coalesce(“default name”)

``

or on a non-OOP/non-chained syntax:

coalesce(a, b, c, …)

coalesce(params[:user][:name], “default name”)

``

This method saves me a lot of time, so I create it in virtually every project that I have:

application.rb

class Object
def coalesce(arg)
self.blank? ? arg : self
end
end

``

Ex.:

2.coalesce(1)
=> 2
nil.coalesce(1)
=> 1

``

The complete version that I use is that:

class Object
def coalesce(obj, *args)
args.unshift(obj) # “obj” is to force at least 1 argument
args.unshift(self) if self.class != Object # non-chained use
result = args.shift
args.each do |arg|
if result.blank?
result = arg
else
break
end
end
result
end
alias_method :clsc, :coalesce
end

``

This complete version allows me to use with all these syntax:

coalesce(1, 2)
coalesce(1, 2, 3)
1.coalesce(2)
1.coalesce(2, 3)
clsc(1, 2)

``

My question is: there is a native “coalesce” method (or something similar) in Ruby or Rails? I’m afraid to reinventing the wheel.

PS: a || b is not a valid answer because “” || “x” returns “” (and the main use for this is with strings).

Thanks,

Daniel Loureiro

http://www.learnwithdaniel.com

a.presence || b

<http://api.rubyonrails.org/classes/Object.html#method-i-presence>

Hi everyone,

it’s a silly question (and I’m kind of ashamed to ask it), but I frequently must do things like that:

a.present? ? a : b

a.presence || b

Whoa! Thank you Scott, you save my day.