Ios 长的UIButton标题标签在中间而不是右侧截断

我正在测试以下代码：

username = @"addagkagalkjagjalggxxaklgjagjglkjag";

NSString *fullUsername = [NSString stringWithFormat:@"%@%@", @"@", username];

UIButton *usernameButton = [UIButton buttonWithType:UIButtonTypeSystem];
[usernameButton setTitle:fullUsername forState:UIControlStateNormal];

usernameButton.frame = CGRectMake(100.0, 10.0, 215.0, 25.0);

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最终结果将截断标签中心的椭圆。我希望它在结尾，但我必须为此设置什么属性？

对于Swift 5和iOS 12.3，

UILabel

有一个名为的属性

lineBreakMode

具有以下声明：

usernameButton.titleLabel.lineBreakMode = NSLineBreakByTruncatingTail;

var lineBreakMode: NSLineBreakMode { get set }

用于包装和截断标签文本的技术

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下面的代码显示了如何使用

NSLineBreakMode设置
lineBreakMode
。通过截断tail

值来截断右侧的

ui按钮的标题标签：

import UIKit
import PlaygroundSupport

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = .white

        let button = UIButton(type: .system)
        button.setTitle("Lorem ipsum dolor sit amet, consectetur adipiscing elit", for: .normal)
        button.titleLabel?.lineBreakMode = NSLineBreakMode.byTruncatingTail

        view.addSubview(button)

        button.translatesAutoresizingMaskIntoConstraints = false
        button.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        button.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
        button.widthAnchor.constraint(equalToConstant: 100).isActive = true
    }

}

PlaygroundPage.current.liveView = ViewController()