Creating objects

ruby-talk
1

i know that in PHP it is possible to do the following:

$class_name = 'User';
$$class_name->new()

but I want to do this in ruby like this perhaps:

@class_name = 'User'
@class_name.new

What is this called and is it possible in ruby. Or is there an
alternative to creating objects from just the class name?

-felix

2

Felix McCoey wrote:

i know that in PHP it is possible to do the following:

$class_name = 'User';
$$class_name->new()

but I want to do this in ruby like this perhaps:

@class_name = 'User'
@class_name.new

What is this called and is it possible in ruby. Or is there an
alternative to creating objects from just the class name?

You can always use const_get:

   class_name = 'User'
   klass = Object.const_get(class_name)
   obj = klass.new

Hope this helps...

Hal

3

Also, if you can create a string of code that does what you want, you can always eval() it:

obj = eval("#{class_name}.new")

But the const_get solution is better. It works because classes are live objects that are stored in global constants.

Josh

···

On Oct 3, 2005, at 11:45 PM, Hal Fulton wrote:

Felix McCoey wrote:

i know that in PHP it is possible to do the following:
$class_name = 'User';
$$class_name->new()
but I want to do this in ruby like this perhaps:
@class_name = 'User'
@class_name.new
What is this called and is it possible in ruby. Or is there an
alternative to creating objects from just the class name?

You can always use const_get:

  class_name = 'User'
  klass = Object.const_get(class_name)
  obj = klass.new

4

@class_name = User
@class_name.new

-or-

@class_name = "User"
eval @class_name+".new"

···

On 10/3/05, Hal Fulton <hal9000@hypermetrics.com> wrote:

Felix McCoey wrote:
> i know that in PHP it is possible to do the following:
>
> $class_name = 'User';
> $$class_name->new()
>
> but I want to do this in ruby like this perhaps:
>
> @class_name = 'User'
> @class_name.new
>

5

Adam Shelly <adam.shelly@gmail.com> writes:

···

On 10/3/05, Hal Fulton <hal9000@hypermetrics.com> wrote:

Felix McCoey wrote:
> i know that in PHP it is possible to do the following:
>
> $class_name = 'User';
> $$class_name->new()
>
> but I want to do this in ruby like this perhaps:
>
> @class_name = 'User'
> @class_name.new
>

@class_name = User
@class_name.new

-or-

@class_name = "User"

eval(@class_name).new

--
Christian Neukirchen <chneukirchen@gmail.com> http://chneukirchen.org