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comp.lang.ruby

extending a class

Luca Scaljery

6/22/2008 8:56:00 PM

Hi All

I'm trying to add methods to a class like:

class Person
def refresh
p "refresh"
end
def dup
P "DUP"
end

TIMED_M = [:refresh, :dup]
TIMED_M.each do |method|
p method
alias_method :"#{method}_without_timing", method

define_method :"{#method}_with_timing" do
p "timing"
start_time = Time.now.to_f
returning(self.send(:"#{method}_without_timing")) do
end_time = Time.now.to_f
puts "#{method}: #{"%.3f" % (end_time - start_time)} s."
end
end
end
end

class << Person
def start_trace
TIMED_M.each do |method|
p "x"
alias_method method, :"#{method}_with_timing"
end
end
end
p = Person.new
p.refresh
Person.start_trace
p.refresh

For some unknown reason I get the following error:
:refresh
:dup
"refresh"
/t2.rb:31:in `start_trace': uninitialized constant Class::TIMED_METHODS
(NameError)
from ./t2.rb:39

Any suggestions why I get this error ?

thnx a lot
LuCa
--
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2 Answers

David A. Black

6/22/2008 9:28:00 PM

0

Hi --

On Mon, 23 Jun 2008, Luca Scaljery wrote:

> Hi All
>
> I'm trying to add methods to a class like:
>
> class Person
> def refresh
> p "refresh"
> end
> def dup
> P "DUP"
> end
>
> TIMED_M = [:refresh, :dup]
> TIMED_M.each do |method|
> p method
> alias_method :"#{method}_without_timing", method
>
> define_method :"{#method}_with_timing" do
> p "timing"
> start_time = Time.now.to_f
> returning(self.send(:"#{method}_without_timing")) do
> end_time = Time.now.to_f
> puts "#{method}: #{"%.3f" % (end_time - start_time)} s."
> end
> end
> end
> end
>
> class << Person
> def start_trace
> TIMED_M.each do |method|
> p "x"
> alias_method method, :"#{method}_with_timing"
> end
> end
> end
> p = Person.new
> p.refresh
> Person.start_trace
> p.refresh
>
> For some unknown reason I get the following error:
> :refresh
> :dup
> "refresh"
> ./t2.rb:31:in `start_trace': uninitialized constant Class::TIMED_METHODS
> (NameError)
> from ./t2.rb:39
>
> Any suggestions why I get this error ?

Here's a boiled-down version:

irb(main):001:0> class C; X = 1; end
=> 1
irb(main):002:0> class << C; X; end
NameError: uninitialized constant Class::X

The reason is that there's no constant X in the singleton class of C.

I also suspect that what's above is not actually cut-and-pasted, since
you don't actually use "TIMED_METHODS" anywhere :-)


David

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Luca Scaljery

6/23/2008 6:15:00 PM

0

David A. Black wrote:
> Hi --
>
> On Mon, 23 Jun 2008, Luca Scaljery wrote:
>
>> end
>> end_time = Time.now.to_f
>> alias_method method, :"#{method}_with_timing"
>> :dup
>> "refresh"
>> ./t2.rb:31:in `start_trace': uninitialized constant Class::TIMED_METHODS
>> (NameError)
>> from ./t2.rb:39
>>
>> Any suggestions why I get this error ?
>
> Here's a boiled-down version:
>
> irb(main):001:0> class C; X = 1; end
> => 1
> irb(main):002:0> class << C; X; end
> NameError: uninitialized constant Class::X
>
> The reason is that there's no constant X in the singleton class of C.
>
> I also suspect that what's above is not actually cut-and-pasted, since
> you don't actually use "TIMED_METHODS" anywhere :-)
>
>
> David

TIMED_M is used:

class << Person
def start_trace
TIMED_M.each do |method|
p "x"
alias_method method, :"#{method}_with_timing"
end
end

Here 'method' is aliased using TIMED_M
--
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