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Fix example LSP #107

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Fix example LSP #107

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2 changes: 1 addition & 1 deletion README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -2083,7 +2083,7 @@ Drawable RenderLargeRectangles(Rectangle rectangles)
{
rectangle.SetWidth(4);
rectangle.SetHeight(5);
var area = rectangle.GetArea(); // BAD: Will return 25 for Square. Should be 20.
var area = rectangle.GetArea(); // BAD: Will return 20 for Square. Should be 25.
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Your are wrong. BAD example - correct.

  • Square.SetHeight(5) set Width and Height to 5 (overwrite Width from 4).
  • Rectangle,GetArea calculare Width * Height = 25
    Good example fix i - different GetArea() with one SetLength

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I just ran it and it gives 20, 20, 20 as result. The right approach would be to overrite the Rectangle::SetWidth() and Rectangle::SetHeight() in Square implementation.

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@dmitryvhf dmitryvhf Jan 16, 2022 •
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You right. Code result is 20. But i sure, this must be return 25 for BAD example.
But as fact - this LSP examples incorrect. This code is not executable. Alot errors, types, missed signatures and etc.

All problems into RenderLargeRectangles method. This cant be in correct code.

  • This must be only render. But now this change sizes.
  • In foreach object cast to Rectangle. Sure we cant set sizes for square.
    Initialization of array must be into main block. This normaly for simple example.
Rectangle rectangle1 = new Rectangle();
rectangle1.SetWidth(2);
rectangle1.SetHeight(3);

Rectangle rectangle2 = new Rectangle();
rectangle2.SetWidth(4);
rectangle2.SetHeight(5);

Square square = new Square();
square.SetWidth(4);
square.SetHeight(5);

var rectangles = new[] { rectangle1, rectangle2, square };
RenderLargeRectangles(rectangles);

BAD:

  • RenderLargeRectangles(Rectangle rectangles) -> Rectangle[] rectangles
  • SetWidth, SetHeight must have return type is void or double.
  • Render() signature is void. Drawable not used into examples.

GOOD:

  • RenderLargeRectangles: parameter must be ShapeBase of type. And array too.
  • RenderLargeRectangles: for set size we must use casting for each object type:
    ((Square)rectangle).SetLength(5);

and etc. errors.
Can you fix both examples?

rectangle.Render(area);
}
}
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