From: Chris Gernon <kabigon@...>
Date: 2007-01-13T06:35:59+09:00
Subject: Re: What does this mean? ||=

Justin Ko wrote:
> I'm looking at this method and don't understand what ||= means:

Much like 'x += 1' is a shortcut for 'x = x + 1', 'x ||= 1' is a 
shortcut for 'x = x || 1'.

The significance of this is that the || method doesn't simply return a 
boolean value; it checks the first argument, returns it if it evaluates 
to 'true' (i.e. is something other than false or nil), and otherwise 
returns the second argument. So it's commonly used as a shortcut for an 
if/then statement, checking if the first argument is nil (or false). So 
the following are all equivalent:

if @account
  @account
else
  Account.find(session[:account_id])
end

is the same as:

@account = @account || Account.find(session[:account_id])

is the same as:

@account ||= Account.find(session[:account_id])

Hope this helps!

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