From: Rodrigo Rosenfeld Rosas Date: 2012-12-08T00:23:12+09:00 Subject: [ruby-core:50663] Re: [ruby-trunk - Feature #4085] Refinements and nested methods --e89a8ff2561020fa0b04d044c75b Content-Type: text/plain; charset=ISO-8859-1 Not all column names can be represented as method names. Or can they? Even if they could I don't like this approach. Look, I currently maintain an application that has some parts written in Grails, others in plain Java and others in Rails. I can do things even more advanced than what you suggested in Grails thanks to some features in Groovy. But the problem begins when you have some local variable (or method) name that happens to be the same as the column. In such cases the DSL approach doesn't really help and may yield to unexpected results (from a user POV) Em 07/12/2012 11:43, "trans (Thomas Sawyer)" escreveu: > > Issue #4085 has been updated by trans (Thomas Sawyer). > > > =begin > @rosenfeld I think the point was that a better designed API could do: > > records = DB[:some_table]. > where{some_column.like '%A'}. > except{other_column < 3}. > where{another_one.in [3, 6]}. > order{sort_column.desc} > > =end > ---------------------------------------- > Feature #4085: Refinements and nested methods > https://bugs.ruby-lang.org/issues/4085#change-34506 > > Author: shugo (Shugo Maeda) > Status: Assigned > Priority: Normal > Assignee: matz (Yukihiro Matsumoto) > Category: core > Target version: 2.0.0 > > > =begin > As I said at RubyConf 2010, I'd like to propose a new features called > "Refinements." > > Refinements are similar to Classboxes. However, Refinements doesn't > support local rebinding as mentioned later. In this sense, > Refinements might be more similar to selector namespaces, but I'm not > sure because I have never seen any implementation of selector > namespaces. > > In Refinements, a Ruby module is used as a namespace (or classbox) for > class extensions. Such class extensions are called refinements. For > example, the following module refines Fixnum. > > module MathN > refine Fixnum do > def /(other) quo(other) end > end > end > > Module#refine(klass) takes one argument, which is a class to be > extended. Module#refine also takes a block, where additional or > overriding methods of klass can be defined. In this example, MathN > refines Fixnum so that 1 / 2 returns a rational number (1/2) instead > of an integer 0. > > This refinement can be enabled by the method using. > > class Foo > using MathN > > def foo > p 1 / 2 > end > end > > f = Foo.new > f.foo #=> (1/2) > p 1 / 2 > > In this example, the refinement in MathN is enabled in the definition > of Foo. The effective scope of the refinement is the innermost class, > module, or method where using is called; however the refinement is not > enabled before the call of using. If there is no such class, module, > or method, then the effective scope is the file where using is called. > Note that refinements are pseudo-lexically scoped. For example, > foo.baz prints not "FooExt#bar" but "Foo#bar" in the following code: > > class Foo > def bar > puts "Foo#bar" > end > > def baz > bar > end > end > > module FooExt > refine Foo do > def bar > puts "FooExt#bar" > end > end > end > > module Quux > using FooExt > > foo = Foo.new > foo.bar # => FooExt#bar > foo.baz # => Foo#bar > end > > Refinements are also enabled in reopened definitions of classes using > refinements and definitions of their subclasses, so they are > *pseudo*-lexically scoped. > > class Foo > using MathN > end > > class Foo > # MathN is enabled in a reopened definition. > p 1 / 2 #=> (1/2) > end > > class Bar < Foo > # MathN is enabled in a subclass definition. > p 1 / 2 #=> (1/2) > end > > If a module or class is using refinements, they are enabled in > module_eval, class_eval, and instance_eval if the receiver is the > class or module, or an instance of the class. > > module A > using MathN > end > class B > using MathN > end > MathN.module_eval do > p 1 / 2 #=> (1/2) > end > A.module_eval do > p 1 / 2 #=> (1/2) > end > B.class_eval do > p 1 / 2 #=> (1/2) > end > B.new.instance_eval do > p 1 / 2 #=> (1/2) > end > > Besides refinements, I'd like to propose new behavior of nested methods. > Currently, the scope of a nested method is not closed in the outer method. > > def foo > def bar > puts "bar" > end > bar > end > foo #=> bar > bar #=> bar > > In Ruby, there are no functions, but only methods. So there are no > right places where nested methods are defined. However, if > refinements are introduced, a refinement enabled only in the outer > method would be the right place. For example, the above code is > almost equivalent to the following code: > > def foo > klass = self.class > m = Module.new { > refine klass do > def bar > puts "bar" > end > end > } > using m > bar > end > foo #=> bar > bar #=> NoMethodError > > The attached patch is based on SVN trunk r29837. > =end > > > > -- > http://bugs.ruby-lang.org/ > > --e89a8ff2561020fa0b04d044c75b Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable

Not all column names can be represented as method names. Or can they?

Even if they could I don't like this approach. Look, I currently mai= ntain an application that has some parts written in Grails, others in plain= Java and others in Rails. I can do things even more advanced than what you= suggested in Grails thanks to some features in Groovy.

But the problem begins when you have some local variable (or method) nam= e that happens to be the same as the column.

In such cases the DSL approach doesn't really help and may yield to = unexpected results (from a user POV)

Em 07/12/2012 11:43, "trans (Thomas Sawyer)= " <transfire@gmail.com&g= t; escreveu:

Issue #4085 has been updated by trans (Thomas Sawyer).


=3Dbegin
@rosenfeld I think the point was that a better designed API could do:

=A0 records =3D DB[:some_table].
=A0 =A0 where{some_column.like '%A'}.
=A0 =A0 except{other_column < 3}.
=A0 =A0 where{another_o= ne.in [3, 6]}.
=A0 =A0 order{sort_column.desc}

=3Dend
----------------------------------------
Feature #4085: Refinements and nested methods
https://bugs.ruby-lang.org/issues/4085#change-34506

Author: shugo (Shugo Maeda)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: 2.0.0


=3Dbegin
=A0As I said at RubyConf 2010, I'd like to propose a new features calle= d
=A0"Refinements."

=A0Refinements are similar to Classboxes. =A0However, Refinements doesn'= ;t
=A0support local rebinding as mentioned later. =A0In this sense,
=A0Refinements might be more similar to selector namespaces, but I'm no= t
=A0sure because I have never seen any implementation of selector
=A0namespaces.

=A0In Refinements, a Ruby module is used as a namespace (or classbox) for =A0class extensions. =A0Such class extensions are called refinements. =A0Fo= r
=A0example, the following module refines Fixnum.

=A0 =A0module MathN
=A0 =A0 =A0refine Fixnum do
=A0 =A0 =A0 =A0def /(other) quo(other) end
=A0 =A0 =A0end
=A0 =A0end

=A0Module#refine(klass) takes one argument, which is a class to be
=A0extended. =A0Module#refine also takes a block, where additional or
=A0overriding methods of klass can be defined. =A0In this example, MathN =A0refines Fixnum so that 1 / 2 returns a rational number (1/2) instead
=A0of an integer 0.

=A0This refinement can be enabled by the method using.

=A0 =A0class Foo
=A0 =A0 =A0using MathN

=A0 =A0 =A0def foo
=A0 =A0 =A0 =A0p 1 / 2
=A0 =A0 =A0end
=A0 =A0end

=A0 =A0f =3D Foo.new
=A0 =A0f.foo #=3D> (1/2)
=A0 =A0p 1 / 2

=A0In this example, the refinement in MathN is enabled in the definition =A0of Foo. =A0The effective scope of the refinement is the innermost class,=
=A0module, or method where using is called; however the refinement is not =A0enabled before the call of using. =A0If there is no such class, module,<= br> =A0or method, then the effective scope is the file where using is called. =A0Note that refinements are pseudo-lexically scoped. =A0For example,
=A0foo.baz prints not "FooExt#bar" but "Foo#bar" in the= following code:

=A0 =A0class Foo
=A0 =A0 =A0def bar
=A0 =A0 =A0 =A0puts "Foo#bar"
=A0 =A0 =A0end

=A0 =A0 =A0def baz
=A0 =A0 =A0 =A0bar
=A0 =A0 =A0end
=A0 =A0end

=A0 =A0module FooExt
=A0 =A0 =A0refine Foo do
=A0 =A0 =A0 =A0def bar
=A0 =A0 =A0 =A0 =A0puts "FooExt#bar"
=A0 =A0 =A0 =A0end
=A0 =A0 =A0end
=A0 =A0end

=A0 =A0module Quux
=A0 =A0 =A0using FooExt

=A0 =A0 =A0foo =3D Foo.new
=A0 =A0 =A0foo.bar =A0# =3D> FooExt#bar
=A0 =A0 =A0foo.baz =A0# =3D> Foo#bar
=A0 =A0end

=A0Refinements are also enabled in reopened definitions of classes using =A0refinements and definitions of their subclasses, so they are
=A0*pseudo*-lexically scoped.

=A0 =A0class Foo
=A0 =A0 =A0using MathN
=A0 =A0end

=A0 =A0class Foo
=A0 =A0 =A0# MathN is enabled in a reopened definition.
=A0 =A0 =A0p 1 / 2 =A0#=3D> (1/2)
=A0 =A0end

=A0 =A0class Bar < Foo
=A0 =A0 =A0# MathN is enabled in a subclass definition.
=A0 =A0 =A0p 1 / 2 =A0#=3D> (1/2)
=A0 =A0end

=A0If a module or class is using refinements, they are enabled in
=A0module_eval, class_eval, and instance_eval if the receiver is the
=A0class or module, or an instance of the class.

=A0 =A0module A
=A0 =A0 =A0using MathN
=A0 =A0end
=A0 =A0class B
=A0 =A0 =A0using MathN
=A0 =A0end
=A0 =A0MathN.module_eval do
=A0 =A0 =A0p 1 / 2 =A0#=3D> (1/2)
=A0 =A0end
=A0 =A0A.module_eval do
=A0 =A0 =A0p 1 / 2 =A0#=3D> (1/2)
=A0 =A0end
=A0 =A0B.class_eval do
=A0 =A0 =A0p 1 / 2 =A0#=3D> (1/2)
=A0 =A0end
=A0 =A0B.new.instance_eval do
=A0 =A0 =A0p 1 / 2 =A0#=3D> (1/2)
=A0 =A0end

=A0Besides refinements, I'd like to propose new behavior of nested meth= ods.
=A0Currently, the scope of a nested method is not closed in the outer metho= d.

=A0 =A0def foo
=A0 =A0 =A0def bar
=A0 =A0 =A0 =A0puts "bar"
=A0 =A0 =A0end
=A0 =A0 =A0bar
=A0 =A0end
=A0 =A0foo =A0#=3D> bar
=A0 =A0bar =A0#=3D> bar

=A0In Ruby, there are no functions, but only methods. =A0So there are no =A0right places where nested methods are defined. =A0However, if
=A0refinements are introduced, a refinement enabled only in the outer
=A0method would be the right place. =A0For example, the above code is
=A0almost equivalent to the following code:

=A0 =A0def foo
=A0 =A0 =A0klass =3D self.class
=A0 =A0 =A0m =3D Module.new {
=A0 =A0 =A0 =A0refine klass do
=A0 =A0 =A0 =A0 =A0def bar
=A0 =A0 =A0 =A0 =A0 =A0puts "bar"
=A0 =A0 =A0 =A0 =A0end
=A0 =A0 =A0 =A0end
=A0 =A0 =A0}
=A0 =A0 =A0using m
=A0 =A0 =A0bar
=A0 =A0end
=A0 =A0foo =A0#=3D> bar
=A0 =A0bar =A0#=3D> NoMethodError

=A0The attached patch is based on SVN trunk r29837.
=3Dend



--
http://bugs.ruby-l= ang.org/

--e89a8ff2561020fa0b04d044c75b--