Robert Klemme
4/21/2007 11:03:00 AM
On 21.04.2007 12:52, yc wrote:
> Hi,
> I am beginner in Ruby.
> I wonder why the following doesn't work.
>
>
> class << Float
> public
> def format(args)
> puts "self=#{self}"
> puts "args=#{args}"
> Kernel.format(args, self)
> end
> end
> puts 45.5678.format("%.02f")
> Gives private method `format' called for 45.5678:Float (NoMethodError)
You are defining a class instance method and trying to call an instance
method. What you are really calling is this:
$ ruby -e 'p method(:format)'
#<Method: Object(Kernel)#format>
You would have to invoke your method as
Float.format(...)
However, given the fact that you can also do
$ ruby -e 'p "%.02f" % 1234'
"1234.00"
I don't see any reason why you would define the method you are trying to
define. If you insist, you should do
irb(main):001:0> class Float
irb(main):002:1> def format(s) s % self end
irb(main):003:1> end
=> nil
irb(main):004:0> 1.234.format "%.02f"
=> "1.23"
irb(main):005:0> 1.0.format "%.02f"
=> "1.00"
Kind regards
robert