swift - 使用选择矩形(:) with UITextField subclass

Question

我有一个 UITextField 子类，我在其中覆盖左 View 、文本和插入符号的绘图矩形。这是使用 leftViewRect(forBounds:)、leftViewRect(forBounds:)、caretRect(for:) 等完成的。一切都按预期工作。

问题是，因为我在 caretRect(for:) 中将绘图矩形(向上)移动 -2 点，所以所选文本的绘图矩形比应有的位置低 2 点。我尝试重写 selectionRects(for:)，但 UITextSelectionRect 的 rect 是仅获取属性。实现这一目标的正确方法是什么？

代码

public override func selectionRects(for range: UITextRange) -> [UITextSelectionRect] {
    super.selectionRects(for: range).map {
        var selectionRect = $0
        selectionRect.rect.origin.y -= 2 // Left side of mutating operator isn't mutable: 'rect' is a get-only property
        return selectionRect
    }
}

Answer 1

根据 rmaddy 的评论和 this answer ，我通过子类化 UITextSelectionRect 并使用修改后的 rect 传入来自 super.selectionRects(for: range) 的映射值来解决这个问题。这就是我的结论:

public final class MyUITextField: UITextField {
    public override func selectionRects(for range: UITextRange) -> [UITextSelectionRect] {
        super.selectionRects(for: range).map {
            MyTextSelectionRect(
                rect: CGRect(x: $0.rect.origin.x, y: $0.rect.origin.y - 2, width: $0.rect.width, height: $0.rect.height),
                writingDirection: $0.writingDirection,
                containsStart: $0.containsStart,
                containsEnd: $0.containsEnd,
                isVertical: $0.isVertical
            )
        }
    }

    //...
}

public final class MyTextSelectionRect: UITextSelectionRect {
    public override var rect: CGRect { _rect }
    public override var writingDirection: NSWritingDirection { _writingDirection }
    public override var containsStart: Bool { _containsStart }
    public override var containsEnd: Bool { _containsEnd }
    public override var isVertical: Bool { _isVertical }

    private let _rect: CGRect
    private let _writingDirection: NSWritingDirection
    private let _containsStart: Bool
    private let _containsEnd: Bool
    private let _isVertical: Bool

    public init(
        rect: CGRect,
        writingDirection: NSWritingDirection,
        containsStart: Bool,
        containsEnd: Bool,
        isVertical: Bool
    ) {
        _rect = rect
        _writingDirection = writingDirection
        _containsStart = containsStart
        _containsEnd = containsEnd
        _isVertical = isVertical
    }
}