ignore_nil

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= ignore_nil {}

== DESCRIPTION

ignore_nil lets you happily ignore nil methods on long method chains. Keeps code pretty and much safer than "rescue nil", since it only catches NoMethodError on nil objects.

ignore_nil {} will either return the last thing evaluated in the block, or nil if a NoMethodError is raised calling a method on a nil object. Any other exceptions raised in the block are not handled, and left for the application to resolve. More details below.

== INSTALLATION

as a gem:

sudo gem install ignore_nil

as a plugin:

script/plugin install git://github.com/ssoroka/ignore_nil.git

== USAGE

ignore_nil { user.profile.photo }

which is much cleaner than, say,

user && user.profile && user.profile.photo

and much much safer than

user.profile.photo rescue nil

which will eat any error, even if it's one you really want to see.

== TELL ME MORE!

The plugin is really rather simple; here's the ignore_nil method:

def ignore_nil(&block)
  begin
    yield
  rescue NoMethodError, RuntimeError => e
    if (e.message =~ /You have a nil object when you didn't expect it/) ||
        (e.message =~ /undefined method `.*?' for nil:NilClass/) || (e.message =~ /^Called id for nil/)
      return nil
    else
      raise e
    end
  end
end

What's interesting about this is it catches both NoMethodError and RuntimeError, both of which can occur if a method unexpectedly returned nil and you called a method on it, but ONLY if the error message matches! This means legitimate NoMethodError and RuntimeError messages will not be bothered by ignore_nil, and will still raise in your application as you expect.

I've used this in a production application since about mid/late 2008, I'd consider it very stable. Feedback welcome!

== AUTHOR

Steven Soroka @ssoroka http://blog.stevensoroka.ca