What is the point of object.presence?

Question

In the Rails docs, the example provided for the object.presence method is:

region = params[:state].presence || params[:country].presence || \'US\'
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Answer 1

Here's the point:

''.presence
# => nil

so if params[:state] == '':

region = params[:state].presence || 'US'
# => 'US'
region = params[:state] || 'US'
# => ''

What's more, it works in similar way (that is, returns nil if object is 'empty') on every object that responds to empty? method, for example:

[].presence
# => nil

Here's the documentation, for reference:

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