Ruby: Dynamic setter with inheritance

Question

I'm trying to format hex strings using an inherited format method. I'm a bit of a Ruby-noob, any help is appreciated.

class Bar
  def alter_the_variable attribute_name
    attribute = method(attribute_name)
    formatted = "%.4x" % attribute.call.hex
    puts formatted    # => 00f3
    attribute = formatted   # What I "want" to be able to do, but
                            # doesn't work because attribute is a local variable

    #attribute.owner.send(:h=, formatted)   # Doesn't work either, gives:
                                            # in `send': undefined method `h=' for Foo:Class (NoMethodError)
  end
end

class Foo < Bar
  def initialize
    @h = "f3"
  end

  def h
    @h
  end

  def h= val
    @h = val
  end
end

f = Foo.new
puts f.h    # => f3
f.alter_the_variable :h
puts f.h    # => f3

David Grayson · Accepted Answer · 2011-06-23 01:07:19Z

1

Here's one way to do what you wanted to do:

def alter_the_variable attribute_name
  current_value = send(attribute_name)
  formatted_value = "%.4x" % current_value.hex
  send (attribute_name.to_s+'=').to_sym, formatted_value
end

answered Jun 23, 2011 at 1:07

David Grayson

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1 Comment

roris Over a year ago

I guess that my attribute.owner in front of send was referring to the Foo class, not the Foo instance. Thank you, sir. You are a scholar and a gentleman.

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