Difference between revisions of "Ruby/C3/Object-Oriented-Programming-Methods/English"

• instance methods
• class methods
• accessor methods

• Ubuntu version 12.04
• Ruby1.9.3

Pre-requisites

You must also have knowledge of Linux commands, Terminal and Text-editor.

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Let's go to that directory.

Create a directory named oop-methods and cd into it.

What are instance methods?

Instance methods are those methods that are available to all instances of the class.

Earlier we had studied how to create objects or instances of a class.

Name it instance_methods.rb

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

I have called an initialize method to initialize the instance variables "name" and "price".

Each of them return instance variables "name" and "price" respectively.

Earlier we had studied how to create methods in Ruby.

Shortly, we will see how these methods will be available to all instances.

I have initialized it with a name value and a price value.

puts product_object_1.name

puts product_object_1.price

On invoking these methods, we get the values stored in the instance variables.

ruby instance_methods.rb >> press Enter

Switch to the terminal and type:

ruby instance_methods.rb

and press Enter to see the output.

Namely, laptop and 35,000.

Let us name this object product_object_2.

This time, let us give a different set of values for name and price.

This proves that instance methods are available to all objects of the class Product.

What are class methods

These methods are not available to instances of the class.

There are different ways you can define class methods.

Name it class_methods.rb

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

However, this time I have added an extra argument called description.

I am also using class variables to hold the values unlike instance variables, earlier.

Checkout the class method declaration for name.

Here it is defined using the class name "Product".

Here I have used the "self" keyword.

This time we are also giving a value for the description.

<<PAUSE>>

What are accessor methods

• Ruby uses accessor methods to access data defined within classes.
• Accessor methods comprise of setter methods and getter methods.
• Setter methods set the values.
• Getter methods get those values.

Ruby uses the word attr_accessor to declare these methods.

Name it accessor_methods.rb

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

I have declared attr_accessor for name and price.

That is all that is required to use these types of methods.

I have initialized a Product object.

This is possible because the attr_declaration, by default, creates methods for setting values.

These getter methods were also generated by the declaration of attr_accessor.

Accessor Methods

Thus they can be accessed by different instances of the class Product.

Summary

• instance methods
• class methods and
• accessor methods

Assignment

• Define a class named Temperature
• Write an instance method using Ruby's accessor method syntax.
• This method should calculate the Celsius for the given Fahrenheit.

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