Swift（macOS）：如何将画线代码修改为绘制圆形？

Hey there! Let's work through adjusting your existing macOS line-drawing code to render circles instead—it's simpler than you might think. I'll walk through common AppKit-based drawing scenarios (the standard for macOS app graphics) with concrete examples.

First, a Quick Recap of Typical Line-Drawing Code #

Chances are your line-drawing code looks something like this, implemented in a custom NSView subclass:

override func draw(_ dirtyRect: NSRect) {
    super.draw(dirtyRect)
    
    // Draw a straight line
    let linePath = NSBezierPath()
    linePath.move(to: NSPoint(x: 50, y: 50))
    linePath.line(to: NSPoint(x: 200, y: 200))
    
    NSColor.blue.setStroke()
    linePath.lineWidth = 2
    linePath.stroke()
}

Option 1: Draw a Circle with oval(in:) (Quick & Easy) #

The simplest way to draw a circle is using NSBezierPath(ovalIn:). Pass a square NSRect (equal width and height) to get a perfect circle:

override func draw(_ dirtyRect: NSRect) {
    super.draw(dirtyRect)
    
    // Define square bounds for the circle
    let circleBounds = NSRect(x: 50, y: 50, width: 150, height: 150)
    let circlePath = NSBezierPath(ovalIn: circleBounds)
    
    // Configure stroke (outline)
    NSColor.red.setStroke()
    circlePath.lineWidth = 2
    circlePath.stroke()
    
    // Optional: Add semi-transparent fill
    // NSColor.green.withAlphaComponent(0.5).setFill()
    // circlePath.fill()
}

Option 2: Draw a Circle with addArc() (Precise Control) #

If you need to specify the exact center and radius (instead of bounds), use the addArc(withCenter:radius:startAngle:endAngle:clockwise:) method. For a full circle, set the start angle to 0 and end angle to 360:

override func draw(_ dirtyRect: NSRect) {
    super.draw(dirtyRect)
    
    // Define circle parameters
    let centerPoint = NSPoint(x: 125, y: 125)
    let circleRadius: CGFloat = 75
    
    let circlePath = NSBezierPath()
    // Draw a full 360-degree arc (circle)
    circlePath.addArc(withCenter: centerPoint, 
                      radius: circleRadius, 
                      startAngle: 0, 
                      endAngle: 360, 
                      clockwise: true)
    
    // Style and render
    NSColor.orange.setStroke()
    circlePath.lineWidth = 2
    circlePath.stroke()
    
    // Optional: Add soft fill
    // NSColor.yellow.withAlphaComponent(0.3).setFill()
    // circlePath.fill()
}

Key Differences from Line Drawing #

• Instead of using move(to:) and line(to:), we leverage NSBezierPath's circle-specific methods
• ovalIn: creates an ellipse (or circle) based on rectangular bounds—keep width/height equal for a perfect circle
• addArc gives you direct control over the circle's center point and radius, great for precise placements
• Always set your desired stroke/fill color before calling stroke() or fill() to render the shape

内容的提问来源于stack exchange，提问作者Devid Otladka