Can I "connect" with the instance if it get's instanciated? Because I wanted to do something like:
if not self.respond_to? :each
return false
end
The bit above can be shortened to
return false unless respond_to? :each
There are at least these three options:
1. do not check at all
This is my preferred solution, as it is the simplest and works well.
irb(main):001:0> class Foo
irb(main):002:1> include Enumerable
irb(main):003:1> end
=> Foo
irb(main):004:0> f=Foo.new
=> #<Foo:0x7ff8bff4>
irb(main):005:0> f.map {|x| x+1}
NoMethodError: undefined method `each' for #<Foo:0x7ff8bff4>
from (irb):5:in `map'
from (irb):5
2. check on the class level, this should generally be sufficient
irb(main):001:0> module Checker
irb(main):002:1> def self.included(cl)
irb(main):003:2> cl.instance_method :each
irb(main):004:2> end
irb(main):005:1> end
=> nil
irb(main):006:0> class Baz
irb(main):007:1> include Checker
irb(main):008:1> end
NameError: undefined method `each' for class `Baz'
from (irb):3:in `instance_method'
from (irb):3:in `included'
from (irb):7:in `include'
from (irb):7
irb(main):009:0> Baz
=> Baz
irb(main):010:0> Baz.ancestors
=> [Baz, Checker, Object, Kernel]
irb(main):011:0>
Note that even the exception does not prevent inclusion. But you can react on this and define the method for example.
3. on instantiation, in this case you need to be in the inheritance chain
irb(main):001:0> module Checker
irb(main):002:1> def initialize(*a,&b)
irb(main):003:2> method :each
irb(main):004:2> end
irb(main):005:1> end
=> nil
irb(main):006:0> class Foo
irb(main):007:1> include Checker
irb(main):008:1> def initialize
irb(main):009:2> super
irb(main):010:2> end
irb(main):011:1> end
=> nil
irb(main):012:0> Foo.new
NameError: undefined method `each' for class `Foo'
from (irb):3:in `method'
from (irb):3:in `initialize'
from (irb):9:in `initialize'
from (irb):12:in `new'
from (irb):12
irb(main):013:0>
4. check when individual objects are extended
irb(main):001:0> module Checker
irb(main):002:1> def self.extended(o)
irb(main):003:2> o.method :each
irb(main):004:2> end
irb(main):005:1> end
=> nil
irb(main):006:0> x = Object.new
=> #<Object:0x7ff89f4c>
irb(main):007:0> x.extend Checker
NameError: undefined method `each' for class `Object'
from (irb):3:in `method'
from (irb):3:in `extended'
from (irb):7:in `extend'
from (irb):7
irb(main):008:0>
Kind regards
robert
···
On 21.03.2008 11:15, Leon Bogaert wrote:
from :0
