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From: Kale Davis on 3 Feb 2010 14:10
I am creating a Ruby script that basically:
1) Has a prompt that gets a command string (ex. 'edit user1 15')
2) Parses the string
3) Runs specific command (like 'edit' or 'new')
4) Repeats

From a functional level I know how to make this work, but how do I make
it dynamic in the sense that another user could easily add their own
commands by adding a new subclass?

I was thinking something like this:

class Update < Command
...
end

The problem is I don't know how to dynamically create a new 'Update'
instance if that is the command string (ie 'update user')? I know how to
call a method using 'send' and I guess that would be another approach
maybe, but is there something for classes?

cmd = gets.chomp #ie 'update user'
c = cmd.split(' ')[0].new #simple parsing example
c.run

Thanks for any help!
Kale
--
Posted via http://www.ruby-forum.com/.

From: Marnen Laibow-Koser on 3 Feb 2010 14:13
Kale Davis wrote:
> I am creating a Ruby script that basically:
> 1) Has a prompt that gets a command string (ex. 'edit user1 15')
> 2) Parses the string
> 3) Runs specific command (like 'edit' or 'new')
> 4) Repeats
>
> From a functional level I know how to make this work, but how do I make
> it dynamic in the sense that another user could easily add their own
> commands by adding a new subclass?
>
> I was thinking something like this:
>
> class Update < Command
> ...
> end
>
> The problem is I don't know how to dynamically create a new 'Update'
> instance if that is the command string (ie 'update user')? I know how to
> call a method using 'send' and I guess that would be another approach
> maybe, but is there something for classes?

Classes are objects too. They respond to Object#send.

>
> cmd = gets.chomp #ie 'update user'
> c = cmd.split(' ')[0].new #simple parsing example
> c.run
>
> Thanks for any help!
> Kale

Best,
-- 
Marnen Laibow-Koser
http://www.marnen.org
marnen(a)marnen.org
--
Posted via http://www.ruby-forum.com/.

From: Ben Bleything on 3 Feb 2010 14:23
On Wed, Feb 3, 2010 at 11:10 AM, Kale Davis <kale.davis(a)gmail.com> wrote:
> I am creating a Ruby script that basically:
> 1) Has a prompt that gets a command string (ex. 'edit user1 15')
> 2) Parses the string
> 3) Runs specific command (like 'edit' or 'new')
> 4) Repeats
>
> From a functional level I know how to make this work, but how do I make
> it dynamic in the sense that another user could easily add their own
> commands by adding a new subclass?

You may be interested in a somewhat ancient project of mine called
Linen which does what you're describing:
http://bitbucket.org/laika/linen/src/

I haven't touched that code for years, and it had some issues when I
last worked with it, so I'm not really suggesting you use it, so much
as look at it for ideas of how to do what you want :)

Ben

From: Robert Klemme on 4 Feb 2010 03:14
On 03.02.2010 20:13, Marnen Laibow-Koser wrote:
> Kale Davis wrote:
>> I am creating a Ruby script that basically:
>> 1) Has a prompt that gets a command string (ex. 'edit user1 15')
>> 2) Parses the string
>> 3) Runs specific command (like 'edit' or 'new')
>> 4) Repeats
>>
>> From a functional level I know how to make this work, but how do I make
>> it dynamic in the sense that another user could easily add their own
>> commands by adding a new subclass?
>>
>> I was thinking something like this:
>>
>> class Update < Command
>> ...
>> end
>>
>> The problem is I don’t know how to dynamically create a new 'Update'
>> instance if that is the command string (ie 'update user')? I know how to
>> call a method using 'send' and I guess that would be another approach
>> maybe, but is there something for classes?
>
> Classes are objects too. They respond to Object#send.

For that he first needs the class instance. Something like cl =
Object.const_get("Update") will do. Then you can do whatever you want
to do with it. In this case all classes should probably share a common
interface method, e.g.

class Command
def execute(*args)
raise "Not implemented"
end
end

class Update < Command
def execute(*a)
...
end
end

Kind regards

robert

--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/
From: Josh Cheek on 4 Feb 2010 06:03
[Note: parts of this message were removed to make it a legal post.]

Hi, not completely sure I understand what you are trying to do, but Robert's
post got me interested, and I wanted to try it out.
This is what I came up with: http://gist.github.com/294520

( mirrored at http://pastie.org/private/1gtz2apwaxac2rcgl3xsw because github
is having issues http://twitter.com/github/status/8627608544 )

Hopefully it's helpful, if not, maybe flesh out the example a bit more of
what you want to do, and what you want other people to be able to do.

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