如何获取 UILabel 中最后一个字符的位置？

下面是获取所有标签行的边框并使用左右标签最后一行的边框的方法。行边界是通过迭代行中所有字符的坐标来确定的 - 如果两个字符在 Y 轴上的坐标不同，则它们位于不同的行上。然后我们将这些边界转换为屏幕坐标并绘制虚线

限制：标签必须具有相同的字体大小和文本格式，在测试项目中它们彼此底部对齐

线条边界是可见的，黑线是线条的完整高度，红线是沿着线条基线的边界（这正是绘制虚线所需的）

最终结果

测试项目：https://github.com/schmidt9/TwoLabelsWithLineBetween

//
//  GlyphPositionLabel.swift
//  TwoLabelsWithLineBetween
//

import UIKit

struct TextLineGeometry {
    var fullRect: CGRect // used for debug here
    var baselineRect: CGRect
}

class GlyphPositionLabel: UILabel {
    
    var debug = false
    
    /// See https://stackoverflow.com/a/77427472/3004003
    var linesGeometry: [TextLineGeometry] {
        guard let text, let attributedText, let font, !text.isEmpty else {
            return []
        }
        
        let textContainer = NSTextContainer(size: bounds.size)
        textContainer.lineFragmentPadding  = 0;
        textContainer.maximumNumberOfLines = self.numberOfLines;
        textContainer.lineBreakMode = self.lineBreakMode;

        let textStorage = NSTextStorage(attributedString: attributedText)
        let layoutManager = NSLayoutManager()
        textStorage.addLayoutManager(layoutManager)
        layoutManager.addTextContainer(textContainer)
        
        let baseline = font.ascender
        
        var geometries = [TextLineGeometry]()
        var index = text.startIndex
        var currentRect: CGRect?
        
        while index != text.endIndex {
            let range = index..<text.index(after: index)
            // ignore white spaces
            if text[range].trimmingCharacters(in: .whitespaces).isEmpty {
                index = text.index(after: index)
                continue
            }

            let rect = layoutManager.boundingRect(forGlyphRange: NSRange(range, in: text), in: textContainer)
            index = text.index(after: index)
            
            if currentRect == nil {
                currentRect = rect
            } else if abs(currentRect!.minY - rect.minY) < 1 {
                // glyph on the same line, resize line rect
                currentRect!.size = CGSize(width: rect.maxX, height: currentRect!.height)
            } else {
                let geometry = TextLineGeometry(
                    fullRect: currentRect!,
                    baselineRect: CGRect(origin: currentRect!.origin, size: CGSize(width: currentRect!.width, height: baseline))
                )
                geometries.append(geometry)
                currentRect = rect
            }
        }
        
        let geometry = TextLineGeometry(
            fullRect: currentRect!,
            baselineRect: CGRect(origin: currentRect!.origin, size: CGSize(width: currentRect!.width, height: baseline))
        )
        
        geometries.append(geometry)
        
        return geometries
    }

    override func draw(_ rect: CGRect) {
        super.draw(rect)
        
        if !debug {
            return
        }
        
        linesGeometry.forEach {
            UIColor.black.setStroke()
            let fullPath = UIBezierPath(rect: $0.fullRect)
            fullPath.stroke()
            
            UIColor.red.setStroke()
            let baseLinePath = UIBezierPath(rect: $0.baselineRect)
            baseLinePath.stroke()
        }
    }

}

//
//  ViewController.swift
//  TwoLabelsWithLineBetween
//

import UIKit

class ViewController: UIViewController {

    @IBOutlet var leftLabel: GlyphPositionLabel!
    @IBOutlet var rightLabel: GlyphPositionLabel!
    
    let lineLayerName = "lineLayerName"
    let linePadding: CGFloat = 4
    
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        drawLine()
    }

    func drawLine() {
        leftLabel.debug = false
        rightLabel.debug = false
        
        guard
            let leftLastLineGeometry = leftLabel.linesGeometry.last,
            let rightLastLineGeometry = rightLabel.linesGeometry.last else {
            return
        }
        
        let leftBaselineRect = leftLabel.convert(leftLastLineGeometry.baselineRect, to: view)
        let leftBaselineBottomRightPoint = CGPoint(x: leftBaselineRect.maxX + linePadding, y: leftBaselineRect.maxY)
        
        let rightBaselineRect = rightLabel.convert(rightLastLineGeometry.baselineRect, to: view)
        let rightBaselineBottomLeftPoint = CGPoint(x: rightBaselineRect.minX - linePadding, y: rightBaselineRect.maxY)
        
        for layer in view.layer.sublayers ?? [] {
            if layer.name == lineLayerName {
                layer.removeFromSuperlayer()
                break
            }
        }
        
        let lineLayer = CAShapeLayer()
        lineLayer.lineDashPattern = [4, 2]
        lineLayer.strokeColor = UIColor.gray.cgColor
        lineLayer.lineWidth = 1
        lineLayer.name = lineLayerName
        view.layer.addSublayer(lineLayer)
        
        let linePath = UIBezierPath()
        linePath.move(to: leftBaselineBottomRightPoint)
        linePath.addLine(to: rightBaselineBottomLeftPoint)
        lineLayer.path = linePath.cgPath
    }

}