Expanding TextView

ExpandingTextView.swift

extension UITextView {
    func makeSelfSizing() -> [NSKeyValueObservation] {
        self.isScrollEnabled = false
        NotificationCenter.default.addObserver(self, selector: #selector(didChangeTextViewContent), name: .UITextViewTextDidChange, object: self)
        
        return [
            observe(\UITextView.text, changeHandler: { this, change in
                self.didChangeTextViewContent()
            }),
            observe(\UITextView.attributedText, changeHandler: { this, change in
                self.didChangeTextViewContent()
            })]
    }
    
    
    @objc func didChangeTextViewContent() {
        if !self.isScrollEnabled {
            let unboundedSize = CGSize(width: self.frame.width, height: .infinity)
            let estimatedSize = self.sizeThatFits(unboundedSize)
            self.frame.size = estimatedSize
            self.constraints.forEach { constraint in
                if constraint.firstAttribute == .height {
                    constraint.constant = estimatedSize.height
                }
            }
            
            setNeedsUpdateConstraints()
            setNeedsLayout()
            superview?.setNeedsUpdateConstraints()
            superview?.setNeedsLayout()
        }
    }
}

Note:

• A height constraint must be set to the textview
• When used in a table view cell, calling beginUpdates and endUpdates on the tableView is required.