Upload
others
View
4
Download
0
Embed Size (px)
Citation preview
OOP
Object oriented programming
OOP
Inheritance
Polymorphism
Encapsulation
Class concepts
• Classes can contain:
• Constants
• Delegates
• Events
• Fields
• Constructors
• Destructors
• Properties
• Methods
• Nested classes
Encapsulation
• Public The type or member can be accessed by any other code in the same assembly or another assembly that references it.
• Private The type or member can be accessed only by code in the same class or struct.
• Protected The type or member can be accessed only by code in the same class or struct, or in a class that is derived from that class.
• Internal The type or member can be accessed by any code in the same assembly, but not from another assembly.
Access modifiers
Access modifiers. Combined.
Access modifiers. Protected internal.
Access modifiers. Protected internal.
Access modifiers. Protected internal.
Access modifiers. Auto-property.
Access modifiers. Best practice
• Reasons to prefer public property over public field
• Serialization
• Reflection
• Testing
• Debugging
• Logging
• Used for data binding
Useful keywords
Readonly
declaration or in a constructor
Value is set when instance is created
Const
initialized at the declaration
Value is set once before compiling
Inheritance & Polymorphism
• No multiple inheritance in C#
• Classes can be inherited
• Interfaces can be implemented
Interfaces
• “Can – do” logics
• Interfaces can contain:
– Properties
– Events
– Methods
– Indexers
• Always public
• Cannot be initiated directly
• Classes can implement one or more interfaces
Abstract classes
• “Is a” – logics
• Can contain whatever a usual class can
• Cannot be initialized directly
• Class can inherit only one
• abstract class
Abstract classes vs interfaces
Feature Interface Abstract class
Multiple inheritance A class may inherit several interfaces.
A class may inherit only one abstract class.
Default implementation An interface cannot provide any code, just the signature.
An abstract class can provide complete, default code and/or just the details that have to be overridden.
Access Modfiers An interface cannot have access modifiers for the subs, functions, properties etc everything is assumed as public
An abstract class can contain access modifiers for the subs, functions, properties
Abstract classes vs interfaces
Feature Interface Abstract class
Core VS Peripheral Interfaces are used to define the peripheral abilities of a class. In other words both Human and Vehicle can inherit from a IMovable interface
An abstract class defines the core identity of a class and there it is used for objects of the same type.
Homogeneity If various implementations only share method signatures then it is better to use Interfaces.
If various implementations are of the same kind and use common behaviour or status then abstract class is better to use.
Speed Requires more time to find the actual method in the corresponding classes
Fast
Abstract classes vs interfaces
Feature Interface Abstract class
Adding functionality (Versioning)
If we add a new method to an Interface then we have to track down all the implementations of the interface and define implementation for the new method.
If we add a new method to an abstract class then we have the option of providing default implementation and therefore all the existing code might work properly.
Fields and Constants No fields can be defined in interfaces
An abstract class can have fields and constrants defined
Overriding
Overriding
Inheritance
Composition
Composition over inheritance
• Prefer composition over inheritance
• do not use a compose-always approach
• it's easy to change behavior on the fly with Dependency Injection / Setters with composition
• Inheritance is more rigid
Composition over inheritance
• Inheritance acid rule:
Does TypeB want to expose the complete interface (all public methods no less) of TypeA such that TypeB can be used where TypeA is expected?
• Prefer composition
Does TypeB only want only some/part of the behavior exposed by TypeA?
Multiple interfaces implementation
Implicit implementation
Explicit implementation
Explicit vs implicit implementation
• Implicit always public
• Explicit always private
• No virtual for explicit
• No abstract for explicit
Design patterns
• In software engineering, a design pattern is a general repeatable solution to a commonly occurring problem in software design. A design pattern isn't a finished design that can be transformed directly into code. It is a description or template for how to solve a problem that can be used in many different situations.
Singleton
Lazy initialization
Abstract factory
Other interesting patterns
These patterns you will definitely need:
- Strategy
- Decorator
- Prototype
- Builder
- Facade
- Dependency injection
- Mediator
Generics
Powerful tool since c# 2.0
Point classes:
• Should contain values with floating points
• Should contain integer values
• Should log values every time the coordinates are changed
Generics
Generics
Generics with where
business, evolved.