Which methods does "puts" invoke?

ruby-talk
1

Hi, if I redefine "to_s" or "inspect" methods in String class I still get the
original output when doing:

  puts string

Which String@method is invoked when executing "puts"?

Thanks.

···

--
Iñaki Baz Castillo <ibc@aliax.net>

2

Iñaki Baz Castillo <ibc@aliax.net> writes:

Hi, if I redefine "to_s" or "inspect" methods in String class I still get the
original output when doing:

  puts string

Which String@method is invoked when executing "puts"?

to_s (inspect is called by p)

class Truc
end

=> nil

machin = Truc.new

=> #<Truc:0x55604>

puts machin

#<Truc:0x55604>
=> nil

class Truc
  def to_s
    "to_s called"
  end
end

=> nil

puts machin

to_s called
=> nil

3

Based on my cursory inspection of the internals (in io.c) it doesn't
appear that puts() is actually calling any of String's methods, at
least not in any way that you can override them.

···

On Mon, Mar 30, 2009 at 4:16 PM, Iñaki Baz Castillo <ibc@aliax.net> wrote:

Hi, if I redefine "to_s" or "inspect" methods in String class I still get the
original output when doing:

puts string

Which String@method is invoked when executing "puts"?

4

From the rdoc of IO#puts (http://www.ruby-doc.org/core-1.8.7/classes/
IO.html#M000474) it states that puts "writes the given objects to ios
as with IO#print". So puts calls print.

Further, the rdoc for IO#print ssays that objects passed to it "that
aren‘t strings will be converted by calling their to_s method."

···

On Mar 30, 2:16 pm, Iñaki Baz Castillo <i...@aliax.net> wrote:

Hi, if I redefine "to_s" or "inspect" methods in String class I still get the
original output when doing:

puts string

Which String@method is invoked when executing "puts"?

Thanks.

--
Iñaki Baz Castillo <i...@aliax.net>

--
Rob Olson
http://thinkingdigitally.com

5

Well, I already tested it, and yes, it seems to work if you define to_s method
in some custom class, but note the following:

···

El Lunes 30 Marzo 2009, Eric Jacoboni escribió:

Iñaki Baz Castillo <ibc@aliax.net> writes:
> Hi, if I redefine "to_s" or "inspect" methods in String class I still get
> the original output when doing:
>
> puts string
>
> Which String@method is invoked when executing "puts"?

to_s (inspect is called by p)

>> class Truc
>> end

=> nil

>> machin = Truc.new

=> #<Truc:0x55604>

>> puts machin

#<Truc:0x55604>
=> nil

>> class Truc
>> def to_s
>> "to_s called"
>> end
>> end

=> nil

>> puts machin

to_s called
=> nil

--------
class String
  def to_s
    "hiiiiiii"
  end
end

# s=String.new("qweqwe")
# puts s
qweqwe
nil
-----------

¿?

--
Iñaki Baz Castillo <ibc@aliax.net>

6

Iñaki Baz Castillo <ibc@aliax.net> writes:

--------
class String
  def to_s
    "hiiiiiii"
  end
end

# s=String.new("qweqwe")
# puts s
qweqwe
nil
-----------

Oh yes, you're right... puts doesn't use to_s when called on a String.

7

Eric Jacoboni wrote:

Oh yes, you're right... puts doesn't use to_s when called on a String.

Nor on nil. (It prints "nil", whereas nil.to_s is the empty string)

···

--
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