1. 什么是intrinsicContentSize

Intrinsic Content Size：固有尺寸。

2. 带有边框的UILabel

public class PaddingLabel: UILabel {
    public var padding: UIEdgeInsets = .zero
    
    public override func drawText(in rect: CGRect) {
        super.drawText(in: rect.inset(by: padding))
    }
    
    public override var intrinsicContentSize: CGSize {
        var size = super.intrinsicContentSize
        
        size.width += padding.left + padding.right
        size.height += padding.top + padding.bottom
        
        return size
    }
}

3. 自动高度的UITableView

/// 自适应大小Table View
public class IntrinsicTableView: UITableView {
    public var maxHeigth: CGFloat?
    
    public override var intrinsicContentSize: CGSize {
        
        if let maxHeigth = maxHeigth {
            return CGSize(width: contentSize.width, height: min(contentSize.height, maxHeigth))
        }
        return contentSize
    }
    
    public override func layoutSubviews() {
        super.layoutSubviews()
        invalidateIntrinsicContentSize()
    }
}