c# barcode generator wpf WORKING WITH A DATABASE: ACTIVE RECORD in Font

Paint PDF-417 2d barcode in Font WORKING WITH A DATABASE: ACTIVE RECORD

WORKING WITH A DATABASE: ACTIVE RECORD
Make PDF 417 In None
Using Barcode maker for Font Control to generate, create PDF-417 2d barcode image in Font applications.
www.OnBarcode.com
Encode GS1 - 13 In None
Using Barcode generator for Font Control to generate, create EAN13 image in Font applications.
www.OnBarcode.com
That s a lot of methods! You may get a different number of methods depending on your environment. Don t worry you don t need to memorize all of them; and most of them are private to Active Record and are used internally, so you never even use them. Also, Still, it s important, if for no other reason than to get a sense of what you get for free just by subclassing Active Record. Even though in this case ActiveRecord:: Base is considered the superclass, it sure makes your lowly Article class super, doesn t it (Sorry, enough bad humor.)
Creating Barcode In None
Using Barcode maker for Font Control to generate, create Barcode image in Font applications.
www.OnBarcode.com
Encoding Data Matrix 2d Barcode In None
Using Barcode printer for Font Control to generate, create Data Matrix ECC200 image in Font applications.
www.OnBarcode.com
A CRASH COURSE IN RUBY CLASS DESIGN
UPC Code Encoder In None
Using Barcode drawer for Font Control to generate, create UPC-A Supplement 2 image in Font applications.
www.OnBarcode.com
Code 128 Code Set A Encoder In None
Using Barcode creation for Font Control to generate, create Code128 image in Font applications.
www.OnBarcode.com
Object-oriented programming is all about objects. You create a class that encapsulates all the logic required to create an object, along with its properties and attributes, and use the class to produce new objects, each of which is a unique instance, distinct from other objects of the same class. That may sound a little abstract (and with good reason abstraction, after all, is the name of the game), but if it helps, you can think of a class as being an object factory. The obvious example is that of a car factory. Contained within a car factory are all the resources, tools, workers, and processes required to produce a shiny new car. Each car that comes off the assembly line is unique. The cars may vary in size, color, and shape, or they may not vary from each other much at all. The point is that even if two cars share the exact same attributes, they aren t the same car. You certainly wouldn t expect a change to the color of one car to affect all the others, would you Well, in objectoriented programming, it s not much different. The class is the factory that produces objects, which are called instances of a class. From a single factory, an infinite number of objects can be produced:
Print Code-39 In None
Using Barcode generator for Font Control to generate, create Code 3 of 9 image in Font applications.
www.OnBarcode.com
International Standard Serial Number Creation In None
Using Barcode generation for Font Control to generate, create ISSN - 13 image in Font applications.
www.OnBarcode.com
class Car end car1 = Car.new car2 = Car.new car1 is a Car object, which is to say it s an instance of the class Car. Each car is a different object, created
PDF-417 2d Barcode Encoder In Java
Using Barcode generation for Java Control to generate, create PDF 417 image in Java applications.
www.OnBarcode.com
Creating PDF 417 In VS .NET
Using Barcode drawer for Visual Studio .NET Control to generate, create PDF417 image in .NET applications.
www.OnBarcode.com
by the same factory. Each object knows which class it belongs to (which factory created it), so if you re ever in doubt, you can ask it:
Barcode Reader In VS .NET
Using Barcode scanner for VS .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
Generating DataMatrix In Java
Using Barcode encoder for Eclipse BIRT Control to generate, create ECC200 image in BIRT applications.
www.OnBarcode.com
car2.class #=> Car
Code-39 Recognizer In Visual C#
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
Create Barcode In Visual Basic .NET
Using Barcode printer for VS .NET Control to generate, create Barcode image in .NET framework applications.
www.OnBarcode.com
Your Car class doesn t really do anything that useful it has no attributes. So, let s give it some. You start by giving it a make something like Toyota or Nissan. Of course, you need to define a way to read and write these attributes. You do this by creating aptly named reader and writer methods. Some objectoriented languages refer to these as getters and setters. The two sets of terms are pretty much interchangeable, but Ruby favors the former. Let s add a reader and writer for the make attribute:
Universal Product Code Version A Generation In Java
Using Barcode creator for Android Control to generate, create UPC-A Supplement 2 image in Android applications.
www.OnBarcode.com
2D Drawer In Visual C#.NET
Using Barcode creator for VS .NET Control to generate, create Matrix image in Visual Studio .NET applications.
www.OnBarcode.com
class Car # A writer method. Sets the value of the @make attribute def make=(text) @make = text end # A reader method. Returns the value of the @make attribute def make
Drawing Barcode In Java
Using Barcode drawer for Java Control to generate, create Barcode image in Java applications.
www.OnBarcode.com
Barcode Maker In VS .NET
Using Barcode creator for ASP.NET Control to generate, create Barcode image in ASP.NET applications.
www.OnBarcode.com
WORKING WITH A DATABASE: ACTIVE RECORD
UPC - 13 Creation In None
Using Barcode encoder for Excel Control to generate, create GS1 - 13 image in Excel applications.
www.OnBarcode.com
Generating Code 128A In Java
Using Barcode encoder for Java Control to generate, create Code 128 Code Set C image in Java applications.
www.OnBarcode.com
@make end end
The methods you just defined (make() and make=()) are instance methods. This is because they can be used only on instances of the class, which is to say, the individual objects that have been created from the class. To create a new instance of the Car class, you use the new constructor:
my_car = Car.new
That s all that s required to create a new instance of the class Car in a local variable called my_car. The variable my_car can now be considered a Car object. Although you have a new Car object, you haven t yet given it a make. If you use the reader method you created to ask your car what its make is, you see that it s nil:
Copyright © OnBarcode.com . All rights reserved.