MFMessageComposeViewController 分配返回 nil

文章：

swift
import MessageUI
class ViewController: UIViewController, MFMessageComposeViewControllerDelegate {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        if MFMessageComposeViewController.canSendText() {
            let messageVC = MFMessageComposeViewController()
            messageVC.recipients = ["1234567890"]
            messageVC.body = "Hello, this is a test message."
            messageVC.messageComposeDelegate = self
            present(messageVC, animated: true, completion: nil)
        } else {
            // 设备不支持短信功能的处理
            print("Device does not support sending text messages.")
        }
    }
    
    func messageComposeViewController(_ controller: MFMessageComposeViewController, didFinishWith result: MessageComposeResult) {
        dismiss(animated: true, completion: nil)
        
        // 根据发送结果进行相应的处理
        switch result {
        case .cancelled:
            print("Message sending cancelled.")
        case .sent:
            print("Message sent successfully.")
        case .failed:
            print("Message sending failed.")
        default:
            break
        }
    }
}