Passing the class as an argument

ruby-talk
1

I'm too lazy to figure it out (and a bit hangover).
I have several collections of objects (read over an OLE API) that I transform to arrays of ruby objects.
Against the DRY religion I ended up with several methods similar to the following:

def get_processors col
  ar=Array.new
  count=col.Count
  1.upto(count){|i|
    ar<<Processor.new(col.GetAt(i))
  }
  return ar
end

Now, this begs for the working equivalent of

def get_collection col, _class
  ar=Array.new
  count=col.Count
  1.upto(count){|i|
    ar<<_class.new(col.GetAt(i))
  }
  return ar
end

How do I do it?
(I do know how do it - I think . It's just that the hangover is not helping the search functions of my brain :slight_smile: )

i.e. this would do what I want
def get_collection col, _class
  ar=Array.new
  count=col.Count
  1.upto(count){|i|
    ar<<instance_eval(_class+".new(col.GetAt(i))")
  }
  return ar
end

...but, is there another way?
Cheers,
V.-

···

--
http://www.braveworld.net/riva

____________________________________________________________________
http://www.freemail.gr - äùñåÜí õðçñåóßá çëåêôñïíéêïý ôá÷õäñïìåßïõ.
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2

Damphyr wrote:

I'm too lazy to figure it out (and a bit hangover).
I have several collections of objects (read over an OLE API) that I transform to arrays of ruby objects.
Against the DRY religion I ended up with several methods similar to the following:

def get_processors col
    ar=Array.new
    count=col.Count
    1.upto(count){|i|
        ar<<Processor.new(col.GetAt(i))
    }
    return ar
end

Now, this begs for the working equivalent of

def get_collection col, _class
    ar=Array.new
    count=col.Count
    1.upto(count){|i|
        ar<<_class.new(col.GetAt(i))
    }
    return ar
end

How do I do it?
(I do know how do it - I think . It's just that the hangover is not helping the search functions of my brain :slight_smile: )

i.e. this would do what I want
def get_collection col, _class
    ar=Array.new
    count=col.Count
    1.upto(count){|i|
        ar<<instance_eval(_class+".new(col.GetAt(i))")
    }
    return ar
end

...but, is there another way?

And to clarify (it's just impossible to concentrate today :frowning: ).
Ideally I would like to call

  get_collection(ole_collection,Processor)

which looks nicer than

  get_collection(ole_collection,"Processor")
Cheers,
V.-

···

--
http://www.braveworld.net/riva

____________________________________________________________________
http://www.freemail.gr - äùñåÜí õðçñåóßá çëåêôñïíéêïý ôá÷õäñïìåßïõ.
http://www.freemail.gr - free email service for the Greek-speaking.

3

Hi --

I'm too lazy to figure it out (and a bit hangover).
I have several collections of objects (read over an OLE API) that I transform to arrays of ruby objects.
Against the DRY religion I ended up with several methods similar to the following:

def get_processors col
  ar=Array.new
  count=col.Count

Are you sure you've got Count as a method name? It's possible, but
fairly bizarre.

  1.upto(count){|i|
    ar<<Processor.new(col.GetAt(i))
  }
  return ar
end

Now, this begs for the working equivalent of

def get_collection col, _class
  ar=Array.new
  count=col.Count
  1.upto(count){|i|
    ar<<_class.new(col.GetAt(i))
  }
  return ar
end

I guess col is 1-originating, so you'd have to adapt this, but here it
is with a normal array:

   def get_collection(col, klass)
     col.map {|e| klass.new(e) }
   end

If klass is a string, you'd have to do a const_get on it first:

   klass = Object.const_get(klass)

or the traditional deep version, if it's a nested constant:

   class Module
     def deep_const_get(c)
       c.split("::").inject(self) {|acc,const| acc.const_get(const) }
     end
   end

or some variant thereof.

David

···

On Mon, 21 Nov 2005, Damphyr wrote:

--
David A. Black
dblack@wobblini.net

4

David A. Black wrote:

Hi --

I'm too lazy to figure it out (and a bit hangover). I have several
collections of objects (read over an OLE API) that I transform to
arrays of ruby objects. Against the DRY religion I ended up with
several methods similar to the following:

def get_processors col ar=Array.new count=col.Count

Are you sure you've got Count as a method name? It's possible, but fairly bizarre.

Yeap, we're not talking Ruby objects here. It's an OLE API and it uses some pretty un-ruby names.
So col is an an OLE object missing such nice conveniences like each and collect and map.
Well, assumptions can kill you. The following works as is, so all this was a post with no reason to exist whatsoever.

class P
  attr_reader :c
  def initialize c
    @c=c
  end
  def to_s
    return @c
  end
end
def get_collection col,_class
  ar=Array.new
  col.each{|e|
    ar<<_class.new(e)
  }
  return ar
end

col=["w","o","w"]
ps=get_collection col,P
puts ps
>
w
o
w

If only everything turned out so easy...
V.-

···

On Mon, 21 Nov 2005, Damphyr wrote:

--
http://www.braveworld.net/riva

____________________________________________________________________
http://www.freemail.gr - äùñåÜí õðçñåóßá çëåêôñïíéêïý ôá÷õäñïìåßïõ.
http://www.freemail.gr - free email service for the Greek-speaking.