如何在Swift中创建属性字符串？

---

本文将解释如何在Swift语言中创建属性字符串。在Swift中，如何为字符串应用不同的属性？

在Swift中，我们使用NSAttributedString类来创建属性字符串。

在Swift中，NSAttributedString是一个用于创建和管理属性字符串的类。属性字符串是指应用了附加属性（例如文本颜色、字体和样式）的字符串。

本文将展示属性字符串的不同用例。

基本设置

import UIKit
class TestController: UIViewController {
    private let attributedLabel = UILabel()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        initialSetup()
    }
    private func initialSetup() {
        
        // basic setup
        view.backgroundColor = .white
        navigationItem.title = "NSAttributedString"
        
        
        // attributedLabel customization
        attributedLabel.numberOfLines = 0
        attributedLabel.backgroundColor = UIColor(white: 0, alpha: 0.1)
        
        view.addSubview(attributedLabel)
        attributedLabel.translatesAutoresizingMaskIntoConstraints = false
        attributedLabel.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 30).isActive = true
        attributedLabel.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -30).isActive = true
        attributedLabel.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 30).isActive = true
        attributedLabel.heightAnchor.constraint(equalToConstant: 300).isActive = true
    }
}

解释

在上面的代码中，我们设置了一个名为TestController的视图控制器来显示UILabel类的不同属性文本。

输出

如何为整个字符串应用颜色？

在这个例子中，您将看到如何为整个字符串应用颜色。以下是如何在Swift中创建具有不同属性的NSAttributedString对象的示例：

private func example1() {
   let string = "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book."
   let attributes: [NSAttributedString.Key: Any] = [.foregroundColor: UIColor.red,
   let attributedString = NSAttributedString(string: string, attributes: attributes)
   attributedLabel.attributedText = attributedString
}

输出

如何为整个字符串应用不同的颜色和字体样式？

在这个例子中，您将看到如何为字符串应用不同的颜色和字体样式。以下是如何在Swift中创建具有不同属性的NSAttributedString对象的示例：

private func example2() {
   // first part
   let attributedString = NSMutableAttributedString(string: "This is the first line of black color. We're not applying any attribute to this part of string.",
      attributes: [.foregroundColor: UIColor.black, font: UIFont.systemFont(ofSize: 17)])
        
   // appending new lines
   attributedString.append(NSAttributedString(string: "\n\n"))
        
   // second part
   attributedString.append(NSAttributedString(string: "This part will be in Red color and bold style in the string.", attributes: [.foregroundColor: UIColor.red, .font: UIFont.systemFont(ofSize: 17, weight: .bold)]))
        
   // appending new lines
   attributedString.append(NSAttributedString(string: "\n\n"))
        
   // third part
   attributedString.append(NSAttributedString(string: "This part will be in Brown color and underline style in the string.", attributes: [.foregroundColor: UIColor.brown, .font: UIFont.systemFont(ofSize: 17), .underlineStyle: 1]))
        
   attributedLabel.attributedText = attributedString
}

输出

如何为整个字符串应用行间距？

在许多情况下，您必须为字符串应用一些行间距才能正确显示多行文本。Swift提供NSMutableParagraphStyle类来添加行之间的间距。以下是如何在Swift中将段落样式应用于字符串的示例：

private func example3() {
   let string = "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book."
   let paragraph = NSMutableParagraphStyle()
   paragraph.lineSpacing = 7
   let attributes: [NSAttributedString.Key: Any] = [.foregroundColor: UIColor.red,
      .font: UIFont.systemFont(ofSize: 17),
      .paragraphStyle: paragraph]
   let attributedString = NSAttributedString(string: string, attributes: attributes)
   attributedLabel.attributedText = attributedString
}

输出

结论

在真实的iOS应用程序中，属性字符串是一个非常有用且常用的功能。您可以为字符串应用不同的样式。此外，您还可以将各种样式应用于子字符串。