C#•4mo ago•

1 reply

Question about base class references

visual studiointermediate

My OOP class is a little far in my memory, we probably talked about something like this but its the kind of issue that I run into so rarely that I completely forgot how to solve it (if its possible).
Long story short, I'm making an animation engine that's kind of the C# version of Manim (or, at least, I'm trying to) and I wanted to make an animation which creates a line by interpolating its end point from its start point to whatever the target end point is.
The way an animation works conceptually is that I describe its initialization and finalization

Start()

Start()

and

End()

End()

methods, and then I update the target object's state with the

Update(float dt)

Update(float dt)

method.
The issue (i think, at least) is rooted in the fact that the base

Animation

Animation

class takes in a

FrameObject

FrameObject

(the base class for every object, including

Line

Line

), but the line creation animation takes in a

Line

Line

, since it obviously wouldn't make sense to apply this function to a circle or something.
What I tried doing was something like this

class LineCreate : Animation 
{
    Line l => AssertTargetIsLine(Target);
    Vector2 finalEnd;

    static Line AssertTargetIsLine(FrameObject target) 
    {
        if (target is not Line l)
            throw new Exception("Target object must be a line");
        return l;
    }
    
    public override void Start() 
    {
        finalEnd = l.End;
        l.InterpolateEnd(0, finalEnd);
        base.Start();
    }

    public override void Update(float dt)
    {
        float percent = LocalTime / Duration;
        percent = EaseFunc(percent);
        l.InterpolateEnd(percent, finalEnd);
        base.Update(dt);
    }

    public override void End()
    {
        l.InterpolateEnd(1, finalEnd);
        base.End();
    }
}

class LineCreate : Animation 
{
    Line l => AssertTargetIsLine(Target);
    Vector2 finalEnd;

    static Line AssertTargetIsLine(FrameObject target) 
    {
        if (target is not Line l)
            throw new Exception("Target object must be a line");
        return l;
    }
    
    public override void Start() 
    {
        finalEnd = l.End;
        l.InterpolateEnd(0, finalEnd);
        base.Start();
    }

    public override void Update(float dt)
    {
        float percent = LocalTime / Duration;
        percent = EaseFunc(percent);
        l.InterpolateEnd(percent, finalEnd);
        base.Update(dt);
    }

    public override void End()
    {
        l.InterpolateEnd(1, finalEnd);
        base.End();
    }
}

However, the line isn't updating. I know the issue isn't the methods for moving the endpoint, so i feel that it has to be that the reference is not the same, but i'm not sure what to do to solve this.

Question about base class references

visual studiointermediate

Start()

Start()

and

End()

End()

methods, and then I update the target object's state with the

Update(float dt)

Update(float dt)

method.
The issue (i think, at least) is rooted in the fact that the base

Animation

Animation

class takes in a

FrameObject

FrameObject

(the base class for every object, including

Line

Line

), but the line creation animation takes in a

Line

Line

, since it obviously wouldn't make sense to apply this function to a circle or something.
What I tried doing was something like this

class LineCreate : Animation 
{
    Line l => AssertTargetIsLine(Target);
    Vector2 finalEnd;

    static Line AssertTargetIsLine(FrameObject target) 
    {
        if (target is not Line l)
            throw new Exception("Target object must be a line");
        return l;
    }
    
    public override void Start() 
    {
        finalEnd = l.End;
        l.InterpolateEnd(0, finalEnd);
        base.Start();
    }

    public override void Update(float dt)
    {
        float percent = LocalTime / Duration;
        percent = EaseFunc(percent);
        l.InterpolateEnd(percent, finalEnd);
        base.Update(dt);
    }

    public override void End()
    {
        l.InterpolateEnd(1, finalEnd);
        base.End();
    }
}

class LineCreate : Animation 
{
    Line l => AssertTargetIsLine(Target);
    Vector2 finalEnd;

    static Line AssertTargetIsLine(FrameObject target) 
    {
        if (target is not Line l)
            throw new Exception("Target object must be a line");
        return l;
    }
    
    public override void Start() 
    {
        finalEnd = l.End;
        l.InterpolateEnd(0, finalEnd);
        base.Start();
    }

    public override void Update(float dt)
    {
        float percent = LocalTime / Duration;
        percent = EaseFunc(percent);
        l.InterpolateEnd(percent, finalEnd);
        base.Update(dt);
    }

    public override void End()
    {
        l.InterpolateEnd(1, finalEnd);
        base.End();
    }
}

Question about base class references

Question about base class references

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