Difference between revisions of "Ruby/C3/Object-Oriented-Concept-in-Ruby/English"

• classes
• creating objects
• different ways of defining methods in Ruby

System Requirements

• Ubuntu version 12.04
• Ruby1.9.3

Pre-requisites

If not, for relevant tutorials, please visit our website.

Let's go to that directory.

Everything in Ruby is an object; from a value to a string or number.

It can serve to keep information organized.

An object is an instantiation of a class.

It is followed by the name of the class.

It is delimited with an “end”.

ruby code

end

The name of the class must begin with a capital letter.

Names that contain more than one word should be camelcased.

For example,

• UserInformation
• ProductInformation

The subsequent file names will have underscore separating the words:

• user underscore information
• product underscore information

Name it class_definition.rb

You can pause the tutorial, and type the code as we go through it.

Now let us make the class useful by adding some variables.

And I have assigned a value to it.

Order.instance_variables

Type puts Order dot instance underscore variables.

ruby class_definition.rb

ruby space class underscore definition dot rb

and see the output.

Let us copy and paste the demarcation, just below the line and save it.

You will notice the class variable you defined, also show up.

Which means an object is created from a class.

An object will have the properties and methods defined in the class.

We declare an object of a class using the new keyword.

Here an object gets created.

product = Product.new

This process is called initialization of an object.

This object is of type : Product.

An initialize method is called at the time of object creation.

On declaring calling new on an object, we invoke the initialize method.

Like other Ruby methods, it is preceded by the “def” keyword.

Let us look at an example.

And name it object_initialize.rb

You can pause the tutorial, and type the code as we go through it.

This will invoke the initialize method.

ruby object_initialize.rb

ruby space object underscore initialize dot rb

and see the output.

It should display the value of the argument passed.

Highlight the line Order.new

Order dot new(“I have created an object”).

Here we have given an argument to the new method.

This argument gets passed on to the initialize method.

ruby space object underscore initialize dot rb

and see the output.

Now, you would have understood what object initialization means.

Each method in a class is defined within the “def” and “end” block.

A multiword method name is separated with an underscore.

contd...

• ? (question-mark)
• = (equal to)

Each of the characters add some meaning to the method.

Let us look at some examples.

And name it class underscore methods dot rb

You can pause the tutorial, and type the code as we go through it.

They are both defined with the “def” and “end” keywords.

Then highlight animal.breathe and then

animal.walk

I have assigned it to a variable called “animal” with lowercase “a”.

Then I have invoked the methods “breathe” and “walk” consequtively.

ruby class_methods.rb

Switch to the terminal and type

ruby class underscore methods dot rb

and see the output.

“ I breathe”

“ I walk”

printed out.

This is because you have invoked the two methods “breathe” and “walk”.

A “puts” statement defined within these methods gives the results you see.

And name it class underscore methods underscore with underscore trailing underscore characters dot rb

You can pause the tutorial, and type the code as we go through it.

Here the breathe method has a trailing “question mark (?)”.

Such methods are generally used to return boolean values.

This is based on the method naming convention of Ruby.

ruby class_methods_with_trailing_characters.rb

ruby space class underscore methods underscore with underscore trailing underscore characters dot rb

and see the output.

“true”

Let us place an equal-to sign (“=(value)”) beside it.

Llet us invoke this method by calling animal dot walk.

Then let us execute this method.

ruby class_methods_with_trailing_characters.rb

ruby class underscore methods underscore with underscore trailing underscore characters dot rb

and see the output.

This is because the equal to sign has another meaning.

animal.walk = “ hops”

So, let us invoke the method a little differently this time.

Type puts animal dot walk equal to “ hops”

ruby class_methods_with_trailing_characters.rb

Now you should be able to write your own methods.

Summary

• How to declare classes
• How to create objects of a class
• Different ways of defining methods in Ruby

Assingment

• Define a class Product
• Define methods that you can use to get values of “myvar” and set values for “myvar”.
• To set values, define the method using “=” sign.
• Instantiate the object of the class and set and get values using the above 2 methods.

About the Spoken Tutorial Project

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Acknowledgements

It is supported by the National Mission on Education through ICT, MHRD, Government of India.

More information on this Mission is available at:

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