To build a strong class in Delphi, you should follow these best practices:
- Use encapsulation to hide implementation details and protect the internal state of the class.
- Use inheritance to create a hierarchy of related classes, and override virtual methods to customize the behavior of derived classes.
- Use interfaces to define a set of related methods that a class can implement, allowing for flexibility and code reuse.
- Use polymorphism to allow different objects to respond to the same method call in different ways.
- Follow good object-oriented design principles, such as the Single Responsibility Principle (SRP) and the Open-Closed Principle (OCP).
- Use exceptions to handle errors and exceptional circumstances in a structured way.
- Use design patterns to solve common design problems in a consistent and reusable way.
- Write thorough unit tests to ensure that the class is working correctly and to facilitate maintenance and future development.
By following these guidelines, you can create a strong, maintainable, and flexible class in Delphi.
Here is an example of a strong class in Delphi that follows the best practices listed above:
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type TShape = class private FColor: TColor; protected procedure SetColor(const Value: TColor); virtual; public constructor Create; virtual; destructor Destroy; override; function Area: Double; virtual; abstract; property Color: TColor read FColor write SetColor; end; TCircle = class(TShape) private FRadius: Double; protected procedure SetColor(const Value: TColor); override; public constructor Create(ARadius: Double); reintroduce; function Area: Double; override; property Radius: Double read FRadius; end; constructor TShape.Create; begin inherited; FColor := clBlack; end; destructor TShape.Destroy; begin inherited; end; procedure TShape.SetColor(const Value: TColor); begin FColor := Value; end; constructor TCircle.Create(ARadius: Double); begin inherited Create; FRadius := ARadius; end; function TCircle.Area: Double; begin Result := Pi * FRadius * FRadius; end; procedure TCircle.SetColor(const Value: TColor); begin inherited; // Additional code to update the appearance of the circle based on the color change end; |
This example defines a TShape class with an abstract Area method and a Color property. It also defines a TCircle class that inherits from TShape and overrides the Area method to calculate the area of a circle. The TCircle class also has a Radius property and overrides the SetColor method to perform additional behavior when the color of the circle is changed.
The TShape class uses encapsulation to hide its implementation details and protect its internal state. It uses inheritance to create a hierarchy of related classes and overrides virtual methods to customize the behavior of derived classes. The TShape class also uses a constructor and destructor to manage the lifetime of the object.
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