前提:
1、label需要设置numberOfLines = 0
2、label使用传递进入的size渲染
3、label使用传递进入的富文本渲染

与参考文章差异
1、与UI视图(UILabel)解耦，更方便一些，可以做数据预处理
2、swift版
3、采用元祖回调核心数据（文本信息、单行range）

import CoreText
/// 文本处理工具类
class TextHelper: NSObject {

/// 获取行信息
    /// - Parameters:
    ///   - attributedString: 富文本（文字、行高、字体 and so on...）
    ///   - size: 所占尺寸
    /// - Returns: (当行文本，单行range)
    static func getLineInfo(attributedString: NSMutableAttributedString,
                            size: CGSize) -> [(String, NSRange)]? {
        guard let attributes = attributedString.attributes else { return nil }
        
        guard let font = attributes[NSAttributedString.Key.font.rawValue] as? UIFont,
                let fontName = font.fontName as? CFString else { return nil }
        let text = attributedString.string
        
        let realFont = CTFontCreateWithName(fontName, font.pointSize, nil)
        
        guard let cfAttributedString = attributedString as? CFAttributedString  else { return nil }
        let frameSetter = CTFramesetterCreateWithAttributedString(cfAttributedString)
        
        let path = CGMutablePath()
        path.addRect(CGRect.init(origin: .zero, size: size), transform: .identity)
        
        let frame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(CFIndex(0), CFIndex(0)), path, nil)
        
        guard let lines = CTFrameGetLines(frame) as? [CTLine] else { return nil }
        
        var lineArray = [(String, NSRange)]()
        
        for line in lines {
            let lineRef = line
            var lineRange: CFRange? = CTLineGetStringRange(lineRef)
            let range = NSRange(location: lineRange?.location ?? 0, length: lineRange?.length ?? 0)
            let lineString = (text as NSString).substring(with: range)
            lineArray.append((lineString, range))
        }
      
        return lineArray
    }
}

参考文章：https://blog.csdn.net/EmulateStep/article/details/78349093