如何在Swift中从WKWebView获取POST请求正文？

import WebKit

class ViewController: UIViewController, WKNavigationDelegate {
    var webView: WKWebView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let webConfiguration = WKWebViewConfiguration()
        webView = WKWebView(frame: .zero, configuration: webConfiguration)
        webView.navigationDelegate = self
        view = webView
        
        let url = URL(string: "https://example.com")
        let request = URLRequest(url: url!)
        webView.load(request)
    }
    
    // WKNavigationDelegate method
    func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
        if navigationAction.request.httpMethod == "POST" {
            if let httpBody = navigationAction.request.httpBody {
                // 获取POST请求的正文
                let postBody = String(data: httpBody, encoding: .utf8)
                print("POST请求正文：\(postBody ?? "")")
            }
        }
        
        decisionHandler(.allow)
    }
}