Classes

A class is a set of instructions (a blueprint) for building an object. As a class, I can inherit abilities from another class. A class is just an Object.

• Constructor

  Each class may have a constructor. That constructor's method name is a reserved word in Ruby called initialize. This constructor can expect arguments passed into the .new() method. Upon initialization of the Class, the constructor is immediately invoked and any code inside of this method is ran.

• Instance Variables

  An instance variable is just a variable assigned to whatever new object created based on each new class. Instance variables are preceded with @.

Instances

Instances are individual objects created from the blueprint that our Class definition lays out. There are many dogs, but every dog comes from a similar genetic blueprint. In this example, each new dog is a new instance of the Dog class.

Methods

Methods are functions that are owned by an object. Since everything in Ruby is an object, all functions are methods.

• Defining a Method

  We define methods starting with def plus the assigned name and then end with with end

  • Parameters

    A parameter is a variable input that can be used within a method. When we define a method, we also define any parameters that the method will accept - however, we have to use placeholder values to refer to these inputs, since we don't yet know their literal values.

    Later, when we invoke the method, we will pass in arguments, which hold actual data, to replace the placeholder parameters.

• Invoking Method

  We invoke a method using dot notation.

  • Arguments

    A parameter/argument is a variable input that can be used within a method. When we define a method, we also define any parameters that the method will accept - however, we have to use placeholder values to refer to these inputs, since we don't yet know their literal values.

    Later, when we invoke the method, we will pass in arguments, which hold actual data, to replace the placeholder parameters.

• Getter Methods

  To get data in our classes' variables, we need to create getter. This allows us to directly access the data contained in a variable inside of our Class.

• Setter Methods

  Set data in our instance variables, we need to create setter method. This allows us to set a value to a variable owned by a class. Mutator is another word for setter.