Calling a function from a variable.

Dev Shed Forums Sponsor:

July 15th, 2008, 08:58 AM

g_hadgraft

Contributing User

Join Date: Mar 2005

Posts: 169

Time spent in forums: 1 Day 10 h 51 m 14 sec
Reputation Power: 4

Calling a function from a variable.

Hi i am trying to do wsomething in rails i assume is possible as it is in many other languages i want to call a function using a variable if that makes sense. e.g.

Code:

def helloWorld
  puts "Hello World"
end 

func_name = "helloWorld"

func_name();

should result in helloworld being run.

I have had a limited amount of success with this.

Code:

@object = NewsController.new()
@snippet = @object.send $2, @variables

Now i may want to run methods in a variaty of controller. In fact i have a variable which endsup holding news how could i create an object using the variable to find which oject to create?

I hope that all makes sense?

July 15th, 2008, 12:40 PM

L7Sqr

Contributing User

Join Date: Jan 2004

Location: Constant Limbo

Posts: 642

Time spent in forums: 1 Week 3 Days 12 h 48 m 20 sec
Reputation Power: 102

Code:

#!/usr/bin/env ruby


def woo
        puts "W00t!!"
end

send "woo"
eval "woo"

Quote:

Originally Posted by output

W00t!!
W00t!!

I would not suggest the second form (eval) - since it is inherently dangerous. However, if you do not know the context in which the method is defined, you may not be able to send it.

As for your second question

Code:

class Junk
    def me
        puts self.class
    end
end

j = Junk.new

class Trunk < j.class
end

f = Trunk.new
j.me
f.me

Quote:

Originally Posted by output

Junk
Trunk

That might give you want you want. If not, then you can always revert back to the ever dangerous eval

Code:

f = eval "#{j.class}.new"

__________________
-- I'll provide you with reference points; if they dont work, refer to something else.

If you process text, this might make your life a little easier.

July 15th, 2008, 02:51 PM

g_hadgraft

Contributing User

Join Date: Mar 2005

Posts: 169

Time spent in forums: 1 Day 10 h 51 m 14 sec
Reputation Power: 4

Thanks for your help with the first part.

Quote:

Originally Posted by L7Sqr

As for your second question

Code:

class Junk
    def me
        puts self.class
    end
end

j = Junk.new

class Trunk < j.class
end

f = Trunk.new
j.me
f.me

[/code]

As for this unless im missing something, which is definatly possible. I dont see how this helps me. As again it look like i create the functions without using a variable. Let me see if i can explain what i want to do.

Using your example let me try to explain what i want. I have some logic which will may give me two different strings. e.g.

Code:

if logged in
  var = "Trunk"
else 
  var = "Junk"
end

using the variable i want to create an object of Trunk or Junk. I could use an if else statement but due to the nature of what i am trying to do this is impractical as this is primarily to call a class for a plugin system, so everytime a new plugin is created a new elsif statement would need to be added so i want to create an object whose name is stored in a variable.

im not really seeing how your example achieves this. I could be completely wrong and thats exactly what it is doing but i cant see it.

Thanks for your help so far though L7Sqr

July 15th, 2008, 03:53 PM

g_hadgraft

Contributing User

Join Date: Mar 2005

Posts: 169

Time spent in forums: 1 Day 10 h 51 m 14 sec
Reputation Power: 4

Thanks for your help L7Sqr

Using your pointers i was able to get it working, I had to use eval to create the statement but now it works.

heres what i eneded up with.

Code:

	@object = eval "#{namecase($1)}Controller.new"
	@snippet = @object.send $2, @variables

Thread Tools	Search this Thread
Email this Page	Search this Thread: Advanced Search
Display Modes	Rate This Thread
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode	Rate This Thread: