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From: Kenneth     on 7 Jul 2010 09:15
I see. Thanks!
--
Posted via http://www.ruby-forum.com/.

From: Brian Candler on 7 Jul 2010 09:16
user = Object.new
def user.banned?; false; end
def user.activated?; true; end

# Example 3

class Pred
def initialize(sym)
@sym = sym
end
def ===(other)
other.send(@sym)
end
end
def is(sym); Pred.new(sym); end
Banned = is(:banned?)
Activated = is(:activated?)

case user
when Banned; puts "Banned!"
when Activated; puts "Activated!"
end
--
Posted via http://www.ruby-forum.com/.

From: Martin DeMello on 7 Jul 2010 10:18
On Wed, Jul 7, 2010 at 6:23 PM, Kenneth <ken70r(a)gmail.com> wrote:

> I was hoping there would be something like
> case user
> when banned?    then ...
> when activated? then ...
> end
>
> I would like to see something like this but it seems hard to implement.

class User
attr_accessor :banned

def banned?
banned
end

def active?
not banned
end
end

class Symbol
def ===(other)
other.send(self)
end
end

a = User.new
a.banned = true

case a
when :banned? ; puts "banned!"
when :active? ; puts "active!"
end

a.banned = false

case a
when :banned? ; puts "banned!"
when :active? ; puts "active!"
end

martin

From: Benoit Daloze on 7 Jul 2010 13:01
On 7 July 2010 17:18, Martin DeMello <martindemello(a)gmail.com> wrote:
> class User
>  attr_accessor :banned
>
>  def banned?
>    banned
>  end
>
>  def active?
>    not banned
>  end
> end
>
> class Symbol
>  def ===(other)
>    other.send(self)
>  end
> end
>
> a = User.new
> a.banned = true
>
> case a
> when :banned? ; puts "banned!"
> when :active? ; puts "active!"
> end
>
> a.banned = false
>
> case a
> when :banned? ; puts "banned!"
> when :active? ; puts "active!"
> end
>
> martin
>

Quite cool the Symbol#===,
it made me think to Proc#===

Sadly, Proc need always a method to be created (so &:sym can not be
used directly)
But I found a (convoluted) example to use Proc#===

#encoding: utf-8
alias :ë :lambda

def check(user)
case user
when ë(&:banned?)
puts "Banned !"
when ë(&:active?)
puts "This is over-convoluted, but you're fine!"
end
end

user = User.new
user.banned = true
check user
user.banned = false
check user

From: Benoit Daloze on 7 Jul 2010 13:14
On 7 July 2010 15:53, Kenneth <ken70r(a)gmail.com> wrote:
> Hi, the point I was trying to make was sending a boolean method to the
> case.
>
> Let's say I have a User object and it has instance methods banned? and
> activated? They are either true or false.
>
> Instead of doing
> case
> when user.banned?    then ...
> when user.activated? then ...
> end
>
> I was hoping there would be something like
> case user
> when banned?    then ...
> when activated? then ...
> end
>
> I would like to see something like this but it seems hard to implement.

Ah, and if you would absolutely respect the same syntax, it is
possible without changing self (but certainly not a good practice)

def method_missing(meth, *a, &b)
lambda { |obj| obj.send(meth, *a, &b) }
end

case user
when banned?
puts "Banned !"
when activated?
puts "This is insane but you're fine!"
end

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