Dynamic methods

[-j B-]

I have seen examples of catching unkown methods called on a class with
method_missing.
For example:

class Example
def initialize(...)
#...
end

def method_missing(item)
call = item.id2name
process(call)
end
end

But I'm not sure if that is an 'acceptable' way to do things. Also,
suppose that I wanted to add a method dynamically that takes arguments,
is this even possible?
My general thought is allowing functionality to be added to a program
dynamically based on a set of rules in a config file.
Any suggestions are welcome.
Thank you.

 

[Trans]

I have seen examples of catching unkown methods called on a class with
method_missing.
For example:

class Example
def initialize(...)
#...
end

def method_missing(item)
call = item.id2name
process(call)
end

def method_missing(item, *args, &blk)
process(item, *args, &blk) # item is already a symbol
end

end

But I'm not sure if that is an 'acceptable' way to do things. Also,
suppose that I wanted to add a method dynamically that takes arguments,
is this even possible?
My general thought is allowing functionality to be added to a program
dynamically based on a set of rules in a config file.
Any suggestions are welcome.
Thank you.

Also, keep in mind Ruby classes are open. You can add real methods to
them on the fly.

class Example
end

foo = "bar"

Example.class_eval %{
def #{foo}
"#{foo}"
end
}

Example.new.foo #=> "bar"

T.

 

[Marcin Mielżyński]

Also, keep in mind Ruby classes are open. You can add real methods to
them on the fly.

class Example
end

foo = "bar"

Example.class_eval %{
def #{foo}
"#{foo}"
end
}

It's better not to use string evals:

Example.class_eval do
define_method foo do
"#{foo}"
end
end

lopex

 

[Robert Dober]

class A
class << self
alias_method ld_new, :new
def new *args, &block
o = old_new( *args, &block )
o.instance_eval do
def ara; value end
end
o
end
end
end ## this does the trick, simple concise, trivial well we wish it were.
## and there are issues with the alias it is a potential redefeinition disaster

the above really su..., sorry

class A
alias_method ld_init, :initialize
def initialize *args, &blk
old_init( *args, &blk )
instance_eval do
def ara; value end
end
end
end
# the issues remain though, we could apply the method redefintion
hammer Pit and Ara came up with and just redefine initialize like
that, but that would make it about 100 lines I guess

Robert