May 12, 2021 Ruby
3. The variable in the Ruby class
4. Use the new method to create objects in Ruby
5. Custom methods to create Ruby objects
Ruby is the perfect object-oriented programming language. Features of object-oriented programming languages include:
These features are discussed in object-oriented Ruby.
An object-oriented program that involves classes and objects. C lasses are blueprints created by individual objects. In object-oriented terminology, your bike is an example of a bike class.
In the case of a vehicle, it includes wheels, horsepower, fuel or gas tank capacity. T hese properties form the data members of the Vehicle class. With these properties you can distinguish one vehicle from another.
The vehicle can also contain specific functions, such as halting, driving, and speeding. T hese functions form the data members of the Vehicle class. Therefore, you can define classes as a combination of properties and functions.
Class Vehicle is defined as follows:
Class Vehicle { Number no_of_wheels Number horsepower Characters type_of_tank Number Capacity Function speeding { } Function driving { } Function halting { } }
By assigning different values to these data members, you can create different instances of the class Vehicle. F or example, an aircraft has three wheels, a horsepower of 1,000, and a fuel tank capacity of 100 liters. In the same way, a car has four wheels, a horsepower of 200 and a gas canister capacity of 25 liters.
In order to implement object-oriented programming with Ruby, you need to first learn how to create objects and classes in Ruby.
In Ruby, the class always starts with the keyword class, followed by the name of the class. T he first letter of the class name should be capital. Class Customer looks like this:
class Customer end
You can use the keyword end to terminate a class. All data members in the class are somewhere between the class definition and the end keyword.
Ruby provides four types of variables:
Using the class variable @@no_of_customers, you can determine the number of objects created, which determines the number of customers.
class Customer @@no_of_customers=0 end
An object is an instance of a class. N ow you'll learn how to create class objects in Ruby. In Ruby, you can create objects using the class's method new.
Method new is a unique method that is predefined in the Ruby library. The new method belongs to the class method.
The following example creates two objects for the class Customer, cust1 and cust2:
cust1 = Customer. new cust2 = Customer. new
Here, cust1 and cust2 are the names of the two objects. T he object name is followed by an equal sign, followed by the class name, followed by the dot operator and the keyword new.
You can pass parameters to the method new that can be used to initialize class variables.
When you want to declare a new method with parameters, you need to declare the method initialize at the same time as you create the class.
The initialize method is a special type of method that is executed when the new method of a class with parameters is called.
The following example creates the initialize method:
class Customer @@no_of_customers=0 def initialize(id, name, addr) @cust_id=id @cust_name=name @cust_addr=addr end end
In this example, you can declare an initialize method with id, name, and addr as local variables. H ere, def and end are used to define the Ruby method initialize. In a later section, you'll learn more about the method.
In the initialize method, the values of these local variables are passed to the instance variables @cust_id, @cust_name, @cust_addr. Here, the value of the local variable is passed with the new method.
Now you can create an object that looks like this:
cust1=Customer.new("1", "John", "Wisdom Apartments, Ludhiya") cust2=Customer.new("2", "Poul", "New Empire road, Khandala")
In Ruby, functions are called methods. Each method in the class starts with the keyword def, followed by the method name.
Method names always begin with lowercase letters. In Ruby, you can end a method using the keyword end.
The following example defines a Ruby method:
class Sample def function statement 1 statement 2 end end
Here, statement 1 and statement 2 are part of the body of the method function within the class Sample. T hese statements can be any valid Ruby statement. For example, we can use the method puts to output Hello Ruby, as follows:
class Sample def hello puts "Hello Ruby!" end end
The following instance creates an object for the class Sample and calls the hello method:
#!/usr/bin/ruby class Sample def hello puts "Hello Ruby!" end end # 使用上面的类来创建对象 object = Sample. new object.hello
This will produce the following results:
Hello Ruby!
If you want to do more exercises on classes and objects, here's a case study: