Define and call methods in ruby

ruby-talk
1

Hi, I just simply can't figure out how I can define methods and call it
in a class. I've tried(as I read so) the following:

class Myclass
....
method_to_call
....
def method_to_call
   .....
end
end

but just doesn't work. So, please point me out on where I'm doing wrong.
thanks..

···

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Posted via http://www.ruby-forum.com/.

2

Hi --

Hi, I just simply can't figure out how I can define methods and call it
in a class. I've tried(as I read so) the following:

class Myclass
....
method_to_call
....
def method_to_call
  .....
end

but just doesn't work. So, please point me out on where I'm doing wrong.
thanks..

This will get you started:

   class Myclass
     def method_to_call
       puts "Hello!"
     end
   end

   object = Myclass.new
   object.method_to_call

It's the object (the instance of Myclass) that can execute the method.

David

···

On Thu, 11 Sep 2008, Jay Pangmi wrote:

--
Rails training from David A. Black and Ruby Power and Light:
   Intro to Ruby on Rails January 12-15 Fort Lauderdale, FL
   Advancing with Rails January 19-22 Fort Lauderdale, FL *
   * Co-taught with Patrick Ewing!
See http://www.rubypal.com for details and updates!

3

David A. Black wrote:

This will get you started:

   class Myclass
     def method_to_call
       puts "Hello!"
     end
   end

   object = Myclass.new
   object.method_to_call

It's the object (the instance of Myclass) that can execute the method.

David

Thanks David for the help, but just kinda suprised, wouldn't it be for
method that's being called from another class (no offense, just my view
for method calls in the same class then can you please lighten me up a
bit coz I'm new to ruby as well. I mean method calls as:

···

from my lil knowledge of java). If what you are saying is what should be

class myclass
if something then
   do_something
end

#implementation of do_something method.
def do_something
  here something is done..
end
end

Thanks again...
--
Posted via http://www.ruby-forum.com/\.

4

David A. Black wrote:

This will get you started:

   class Myclass
     def method_to_call
       puts "Hello!"
     end
   end

   object = Myclass.new
   object.method_to_call

It's the object (the instance of Myclass) that can execute the method.

David

Thanks David for the help, but just kinda suprised, wouldn't it be for
method that's being called from another class (no offense, just my view
from my lil knowledge of java). If what you are saying is what should be
for method calls in the same class then can you please lighten me up a

What?

bit coz I'm new to ruby as well. I mean method calls as:

class myclass
if something then
  do_something
end

#implementation of do_something method.
def do_something
here something is done..
end
end

You are mixing instance and class methods. When you do

class X
  if expr then
    do_something
  end
end

do_somehing must be a class method because inside class..end self is
the class. Try it out:

class Foo
  p self

  def x
    p self
  end
end

Foo.new.x

From what you write I am unsure whether basic OO principles are clear
to you. In case not, you should probably read some introductory
material about OOA/OOD/OOP.

Cheers

robert

···

2008/9/11 Jay Pangmi <jaeezzy@gmail.com>:

--
use.inject do |as, often| as.you_can - without end

5

You have to distinguish between instance methods and class methods.

You appear to be asking how to create a class method. To do that you use
self.do_something:

class Myclass
  if something then
    do_something
  end

  def self.do_something
    here something is done..
  end
end

6

Hi --

···

On Thu, 11 Sep 2008, Jay Pangmi wrote:

David A. Black wrote:

This will get you started:

   class Myclass
     def method_to_call
       puts "Hello!"
     end
   end

   object = Myclass.new
   object.method_to_call

It's the object (the instance of Myclass) that can execute the method.

David

Thanks David for the help, but just kinda suprised, wouldn't it be for
method that's being called from another class (no offense, just my view
from my lil knowledge of java). If what you are saying is what should be
for method calls in the same class then can you please lighten me up a
bit coz I'm new to ruby as well. I mean method calls as:

class myclass
if something then
  do_something
end

#implementation of do_something method.
def do_something
here something is done..
end

You're defining do_something as an instance method of Myclass; that
means that you need an instance of Myclass in order to call
do_something. To get that instance, you need to do Myclass.new.

David

--
Rails training from David A. Black and Ruby Power and Light:
   Intro to Ruby on Rails January 12-15 Fort Lauderdale, FL
   Advancing with Rails January 19-22 Fort Lauderdale, FL *
   * Co-taught with Patrick Ewing!
See http://www.rubypal.com for details and updates!

7

Hi --

···

On Thu, 11 Sep 2008, DanDiebolt.exe wrote:

You have to distinguish between instance methods and class methods.

You appear to be asking how to create a class method. To do that you use
self.do_something:

class Myclass
if something then
   do_something
end

def self.do_something
   here something is done..
end
end

Though you'd have to define the method before you call it.

David

--
Rails training from David A. Black and Ruby Power and Light:
   Intro to Ruby on Rails January 12-15 Fort Lauderdale, FL
   Advancing with Rails January 19-22 Fort Lauderdale, FL *
   * Co-taught with Patrick Ewing!
See http://www.rubypal.com for details and updates!

8

maybe I'm wrong. but what I'm saying is (Here's what I do in java)

public class myclass
{
.....
String name;
static int i=0;
//defining a instance method
public void setName(String name)
{
   this.name=name;
}
//defining the method.
public void printMessage()
{
   System.out.println("Message");
}
//for some event
public void actionPerformed(ActionEvent e)
{
   if (e.getSource()==xxxx)
   {
     printMessage(); //declaring a method in the same class.
   }
}
........
}

public class anotherclass extends myclass
{
  myclass mc;
  int j;
  ..............
  mc.setName("James"); //calls method with the instance of the class
  j=myclass.i; //here coz i belongs to class.
}

Hope, it clears out what I'm trying to do. Just example, not very good
in java either...
So, what I'm trying to do is declare similar method as printMessage() in
ruby. thanks

···

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Posted via http://www.ruby-forum.com/.

9

David A. Black wrote:

You're defining do_something as an instance method of Myclass; that
means that you need an instance of Myclass in order to call
do_something. To get that instance, you need to do Myclass.new.

David

Thanks again David, So, here's how I've tried:

class MyDate
md=MyDate.new()
md.display
def display
   puts "hi"
end
end

but failed... also with md=MyDate.new if () matters at all..
thanks

···

--
Posted via http://www.ruby-forum.com/\.

10

look at David's original post *again*

···

On Thu, Sep 11, 2008 at 4:37 PM, Jay Pangmi <jaeezzy@gmail.com> wrote:

David A. Black wrote:

You're defining do_something as an instance method of Myclass; that
means that you need an instance of Myclass in order to call
do_something. To get that instance, you need to do Myclass.new.

David

Thanks again David, So, here's how I've tried:

class MyDate
md=MyDate.new()
md.display
def display
  puts "hi"
end
end

11

Jay Pangmi wrote:

maybe I'm wrong. but what I'm saying is (Here's what I do in java)

public class myclass
{
.....
String name;
static int i=0;
//defining a instance method
public void setName(String name)
{
   this.name=name;
}
//defining the method.
public void printMessage()
{
   System.out.println("Message");
}
//for some event
public void actionPerformed(ActionEvent e)
{
   if (e.getSource()==xxxx)
   {
     printMessage(); //declaring a method in the same class.
   }
}
........
}

public class anotherclass extends myclass
{
  myclass mc;
  int j;
  ..............
  mc.setName("James"); //calls method with the instance of the class
  j=myclass.i; //here coz i belongs to class.
}

Hope, it clears out what I'm trying to do. Just example, not very good in java either...
So, what I'm trying to do is declare similar method as printMessage() in ruby. thanks

   A mantra for you.. Ruby is not Java repeat 100 times until you believe it. Then start learning Ruby all over again with a beginner's mind. Java is compiled, Ruby interpreted. Ruby knows nothing of your display method until it sees it.. see my previous post.
R

···

--
Ron Fox
NSCL
Michigan State University
East Lansing, MI 48824-1321

12

Robert Dober wrote:

David A. Black wrote:

You're defining do_something as an instance method of Myclass; that
means that you need an instance of Myclass in order to call
do_something. To get that instance, you need to do Myclass.new.

David

Thanks again David, So, here's how I've tried:

class MyDate
md=MyDate.new()
md.display
def display
  puts "hi"
end
end

look at David's original post *again*

Remember that ruby is interpreted, not compiled. If the interpreter hasn't textually seen a method definition yet, it does not exist.
Add to that the fact that display is a base method in ruby to display prints the contents of an object here's what happens:

md = MyDate.new() makes a new object of type MyDate
md.display Invokes the Object.display method.. but since MyDate has
             no members, there's not much to display

def display ... overrides the Object.display method finally...

Now if you had written:

class MyDate
    def display
      puts "hi"
    end
    md=MyDate.new()
    md.display
  end

Things might be different. Whether you get what you want? That depends a lot on what you want.

Ron

···

On Thu, Sep 11, 2008 at 4:37 PM, Jay Pangmi <jaeezzy@gmail.com> wrote:

--
Ron Fox
NSCL
Michigan State University
East Lansing, MI 48824-1321