UITextView 라인수 계산

UITextView+numberOfLines.swift

import Foundation
import UIKit

public extension UITextView {
    func numberOfLines() -> Int {
        let numberOfGlyphs = base.layoutManager.numberOfGlyphs
        var index = 0, lineCount = 0
        var lineRange = NSRange(location: NSNotFound, length: 0)
        
        while index < numberOfGlyphs {
            base.layoutManager.lineFragmentRect(forGlyphAt: index, effectiveRange: &lineRange)
            index = NSMaxRange(lineRange)
            lineCount += 1
        }
        return lineCount
    }
}