c# barcode generator library open source Shape Abstractions in Font

Painting DataMatrix in Font Shape Abstractions

Shape Abstractions
DataMatrix Generation In None
Using Barcode generation for Font Control to generate, create Data Matrix 2d barcode image in Font applications.
www.OnBarcode.com
Draw GTIN - 12 In None
Using Barcode printer for Font Control to generate, create UPC-A Supplement 2 image in Font applications.
www.OnBarcode.com
If we have a collection of shapes that derive from the common trait OShape that has an area method on it, our object definitions would look something like the following if we used a traditional OOP approach:
Creating Data Matrix In None
Using Barcode creation for Font Control to generate, create DataMatrix image in Font applications.
www.OnBarcode.com
Encode Code 39 Extended In None
Using Barcode maker for Font Control to generate, create Code39 image in Font applications.
www.OnBarcode.com
trait OShape { def area: Double } class OCircle(radius: Double) extends OShape { def area = radius * radius * Math.Pi } class OSquare(length: Double) extends OShape { def area = length * length } class ORectangle(h: Double, w: Double) extends OShape { def area = h * w }
Painting Barcode In None
Using Barcode maker for Font Control to generate, create Barcode image in Font applications.
www.OnBarcode.com
Printing Barcode In None
Using Barcode creator for Font Control to generate, create Barcode image in Font applications.
www.OnBarcode.com
Let s compare this with the pattern-matching implementation:
GS1-128 Creation In None
Using Barcode drawer for Font Control to generate, create GS1 128 image in Font applications.
www.OnBarcode.com
Make Code11 In None
Using Barcode creation for Font Control to generate, create Code 11 image in Font applications.
www.OnBarcode.com
trait Shape case class Circle(radius: Double) extends Shape case class Square(length: Double) extends Shape case class Rectangle(h: Double, w: Double) extends Shape object Shape { def area(shape: Shape): Double = shape match { case Circle(r) => r * r * Math.Pi case Square(l) => l * l case Rectangle(h, w) => h * w } }
Data Matrix 2d Barcode Creator In None
Using Barcode generation for Microsoft Word Control to generate, create ECC200 image in Office Word applications.
www.OnBarcode.com
DataMatrix Maker In Java
Using Barcode printer for BIRT Control to generate, create ECC200 image in BIRT applications.
www.OnBarcode.com
CHAPTER 5 PATTERN MATCHING
Print USS Code 128 In Java
Using Barcode encoder for Android Control to generate, create Code 128 Code Set C image in Android applications.
www.OnBarcode.com
UPC-A Supplement 2 Drawer In C#
Using Barcode maker for Visual Studio .NET Control to generate, create UPC-A image in .NET framework applications.
www.OnBarcode.com
In the pattern-matching example, all of the logic for calculating area is located in the same method, but the fact that the method exists is not obvious from looking at the Shape trait. So far, the OOP methodology seems to be the right answer because it makes obvious what shapes can do. However, if we have a shape library and we want to calculate the perimeter of each of the shapes, there s a benefit to pattern matching:
Printing GTIN - 13 In None
Using Barcode encoder for Online Control to generate, create EAN-13 image in Online applications.
www.OnBarcode.com
UCC - 12 Encoder In Java
Using Barcode drawer for Java Control to generate, create UPC Code image in Java applications.
www.OnBarcode.com
def perimeter(shape: Shape) = shape match { case Circle(r) => 2 * Math.Pi * r case Square(l) => 4 * l case Rectangle(h, w) => h * 2 + w * 2 }
Creating Barcode In .NET
Using Barcode drawer for .NET Control to generate, create Barcode image in Visual Studio .NET applications.
www.OnBarcode.com
Encode Barcode In None
Using Barcode maker for Office Excel Control to generate, create Barcode image in Microsoft Excel applications.
www.OnBarcode.com
In this case, the open data makes implementing the perimeter method possible. With the OOP implementation, we would have to expose data to make the perimeter method possible to implement. So our OOP implementation would look like
QR Code ISO/IEC18004 Creation In Objective-C
Using Barcode generator for iPad Control to generate, create Quick Response Code image in iPad applications.
www.OnBarcode.com
Code 39 Full ASCII Reader In Visual C#
Using Barcode decoder for .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
trait OShape { def area: Double } class def def } class def def } class def def def } OCircle(radius: Double) extends OShape { area = radius * radius * Math.Pi getRadius = radius OSquare(length: Double) extends OShape { area = length * length getLength = length ORectangle(h: Double, w: Double) extends OShape { area = h * w getHeight = h getWidth = w
Printing GS1 - 13 In None
Using Barcode creator for Office Word Control to generate, create UPC - 13 image in Word applications.
www.OnBarcode.com
Making Data Matrix In Java
Using Barcode creator for Java Control to generate, create Data Matrix ECC200 image in Java applications.
www.OnBarcode.com
More broadly, it s rare that the designer of an object hierarchy implements all the methods that a library consumer is going to need. The visitor pattern is a design pattern that allows you to add functionality to a class hierarchy after the hierarchy is already defined. Let s look at a typical visitor pattern implementation. Following is the interface that defines the visitor. The code contains
CHAPTER 5 PATTERN MATCHING
circular class references and will not work at the REPL. So, first the code, and then a walkthrough of the code:
trait def def def def } OCarVisitor { visit(wheel: OWheel): Unit visit(engine: OEngine): Unit visit(body: OBody): Unit visit(car: OCar): Unit
trait OCarElement { def accept(visitor: OCarVisitor): Unit } class OWheel(val name: String) extends OCarElement { def accept(visitor: OCarVisitor) = visitor.visit(this) } class OEngine extends OCarElement { def accept(visitor: OCarVisitor) = visitor.visit(this) } class OBody extends OCarElement { def accept(visitor: OCarVisitor) = visitor.visit(this) } class OCar extends OCarElement { val elements = List(new OEngine, new OBody, new OWheel("FR"), new OWheel("FL"), new OWheel("RR"), new OWheel("RL")) def accept(visitor: OCarVisitor) = (this :: elements).foreach(_.accept(visitor)) }
The library author has to think about extensibility and implement the visitor pattern. Note also that the class hierarchy is fixed in the visitor because the visitor has to implement an interface that defines all the possible classes that the visitor can handle:
trait def def def def } OCarVisitor { visit(wheel: OWheel): Unit visit(engine: OEngine): Unit visit(body: OBody): Unit visit(car: OCar): Unit
Copyright © OnBarcode.com . All rights reserved.