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Date: Mon, 13 May 2013 17:36:41 +1000
Subject: Re: object.enable() anti-pattern
From: Chris Angelico <rosuav@gmail.com>
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Xref: csiph.com comp.lang.python:45226

On Mon, May 13, 2013 at 4:32 PM, F=E1bio Santos <fabiosantosart@gmail.com> =
wrote:
>
> On 13 May 2013 00:22, "Greg Ewing" <greg.ewing@canterbury.ac.nz> wrote:
>> The same argument can be applied to:
>>
>>    foo =3D Foo()
>>    foo.do_something()
>>    foo.enable() # should have done this first
>>
>> You're passing an invalid input to Foo.do_something,
>> namely a Foo that hasn't been enabled yet.
>
> I don't think you can really count that as invalid input in OOP terms. Af=
ter
> all in most languages `self` / `this` / whatever is not an argument to ev=
ery
> method.

Yes, it is; it's just often implicit. C++ lets you poke around with
the internals, and it's pretty clear that 'this' is an argument. (See
for instance what happens with the gcc 'format' attribute - I can't
find a convenient docs page, but it's been mentioned on SO [1] and can
be easily verified.) EMCAScript lets you call any function with any
'this' by using the .call() or .apply() methods - which, in my
extremely not-humble opinionated opinion, is bad design (closures work
implicitly, but the 'this' pointer doesn't??). Python turns an
attribute lookup on an instance into an attribute lookup on the class
plus a currying. One way or another, the bit-before-the-dot is an
argument to the function.

[1] http://stackoverflow.com/questions/11621043/how-should-i-properly-use-a=
ttribute-format-printf-x-y-inside-a-class

ChrisA