1. 效果

2.代码

代码1

class tableViewTestVC: UIViewController{
    lazy var label:UILabel = {
       let label = UILabel()
        label.backgroundColor = .yellow
        let font =  UIFont.init(name: "PingFang SC", size: 14)!
        label.font = font
        label.numberOfLines = 0
        let str:NSString = "但是公司的 高度 是广东省公司的广东省高速度 高度 来开个大帅哥多撒谎"
        label.text = str as String![请添加图片描述](https://img-blog.csdnimg.cn/740d60d35e7d48fca7fb0447d14f3e2c.png?x-oss-process=image/watermark,type_d3F5LXplbmhlaQ,shadow_50,text_Q1NETiBA5pif5pif5pyI5LquMA==,size_12,color_FFFFFF,t_70,g_se,x_16)

        return label
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(label)
        label.snp.makeConstraints { (make) in
            make.top.equalToSuperview().offset(30)
            make.left.equalToSuperview().offset(10)
            make.width.equalTo(200)
        }
        
        let labelText = label.text!
        let range:Range = labelText.range(of: "高度")!
        let nsrange = labelText.nsRange(from: range)

        let mutableAttribute = NSMutableAttributedString(attributedString: label.attributedText!)
        mutableAttribute.addAttributes([NSAttributedString.Key.foregroundColor : UIColor.red, NSAttributedString.Key.font : UIFont.init(name: "PingFang SC", size: 14)!], range: nsrange)
        
        label.attributedText = mutableAttribute
    }
    
}

extension String {
    /// range转换为NSRange
    func nsRange(from range: Range<String.Index>) -> NSRange {
        return NSRange(range, in: self)
    }
}

代码2(推荐)

        func getAttributedString(str1: String, str2: String) -> NSMutableAttributedString {
            var attriText = NSMutableAttributedString(string: str1 + str2)
            let index = str1.count
            attriText.addAttributes([NSAttributedString.Key.foregroundColor : UIColor.black, NSAttributedString.Key.font : UIFont.init(name: "Helvetica-Bold", size: 23)!], range: NSRange(location: 0, length: index))
            attriText.addAttributes([NSAttributedString.Key.foregroundColor : UIColor.black, NSAttributedString.Key.font : UIFont.init(name: "PingFang SC", size: 15)!], range: NSRange(location: index, length: attriText.string.count - index))
            return attriText
        }
        bStepValueLabel.attributedText = getAttributedString(str1: "36", str2: "步")