我要问的是部分与设计模式有关.
可以说我有一个IDrawing界面.
另外两个名为TextDrawing和ShapeDrawing的基本类实现了这个,我有一个知道如何绘制这些类的View类!
但是我有更复杂的绘图类,它们也实现了IDrawing接口,但它们本身由几个IDrawing类组成!
如何在我的View类中绘制这些?显然教会View类来绘制每个新的IDrawing并不是一个好主意!但我还有其他选择吗?也许设计不正确?如何告诉View的Draw方法知道复杂类的原始部分并绘制它们?
public interface IDrawing { } public class TextDrawing : IDrawing { } public class ShapeDrawing : IDrawing { } public class SignDrawing : IDrawing { public TextDrawing Text { get; set; } public ShapeDrawing Border { get; set; } } public class MoreComplexDrawing : IDrawing { public TextDrawing Text { get; set; } public ShapeDrawing Border1 { get; set; } public ShapeDrawing Border2 { get; set; } } public class View { public void Draw(IDrawing drawing) { // The View only kNows how to draw TextDrawing and ShapeDrawing. // These as the primitive building blocks of all drawings. // How can it draw the more complex ones! if (drawing is TextDrawing) { // draw it } else if (drawing is ShapeDrawing) { // draw it } else { // extract the drawings primitive parts (TextDrawing and ShapeDrawing) and draw them! } } }
更新:
我收到了在绘图类中实现Draw()方法的建议.
View中的Draw方法依赖于要绘制的外部库(在我的例子中,它是SkiaSharp库).如果我在这些类中实现Draw,它们将不再是通用的!例如,我将无法在其他项目中使用它们,因为我有不同的策略来绘制东西.
解决方法
我会在接口中添加一个Draw()方法,并在每个类中实现它.
这样做的好处是您的View不关心实际类型是什么.
public interface IDrawing { void Draw(); } public class TextDrawing : IDrawing { public void Draw() { // Draw a TextDrawing } } public class ShapeDrawing : IDrawing { public void Draw() { // Draw a ShapeDrawing } } public class SignDrawing : IDrawing { public TextDrawing Text { get; set; } public ShapeDrawing Border { get; set; } public void Draw() { // Draw a SignDrawing } } public class MoreComplexDrawing : IDrawing { public TextDrawing Text { get; set; } public ShapeDrawing Border1 { get; set; } public ShapeDrawing Border2 { get; set; } public void Draw() { // Draw a MoreComplexDrawing } } public class View { public void Draw(IDrawing drawing) { //Draw the drawing drawing.Draw(); } }
更新 – 摘要对SkiaSharp的依赖
您需要为SkiaSharp创建一个包装器,或者为实际执行绘制的任何外部依赖项创建一个包装器.这应该与IDrawing接口和派生类存在于同一个程序集中.
public interface IDrawingContext { // Lots of drawing methods that will facilitate the drawing of your `IDrawing`s void DrawText(...); void DrawShape(...); void DrawBorder(...); }
以及SkiaSharp的具体实现
public class SkiaSharpDrawingContext IDrawingContext { // Lots of drawing methods that will facilitate the drawing of your IDrawings public void DrawText(...) { /* Drawing code here */ } public void DrawShape(...) { /* Drawing code here */ } public void DrawBorder(...) { /* Drawing code here */ } }
将IDrawing界面更新为
public interface IDrawing { void Draw(IDrawingContext drawingContext); }
更新您的课程以反映此更改.您的类将调用IDrawingContext实现上的方法来进行绘制.
在应用程序中创建特定于依赖项的实现,并更新View类以使用新的SkiaSharpDrawingContext
public class View { public void Draw(IDrawing drawing) { // This should ideally be injected using an IOC framework var drawingContext = new SkiaSharpDrawingContext(...); //Draw the drawing drawing.Draw(drawingContext); } }