Question

我是Swift的新手，我在networkExtension内跟踪此方法的文档：

open class NEVPNConnection : NSObject {
    /*!
         * @method startVPNTunnelAndReturnError:
         * @discussion This function is used to start the VPN tunnel using the current VPN configuration. The VPN tunnel connection process is started and this function returns immediately.
         * @param error If the VPN tunnel was started successfully, this parameter is set to nil. Otherwise this parameter is set to the error that occurred. Possible errors include:
         *    1. NEVPNErrorConfigurationInvalid
         *    2. NEVPNErrorConfigurationDisabled
         * @return YES if the VPN tunnel was started successfully, NO if an error occurred.
         */
        @available(iOS 8.0, *)
        open func startVPNTunnel() throws

我理解它的方式，如果它返回true，则建立VPN连接。

这是我的代码：

                    let result: Bool?
                    do {
                        result = try self.vpnManager.connection.startVPNTunnel()
                        if result! {
                            NotificationCenter.default.post(name: .enableDisconnect, object: nil)
                        }
                    } catch let error {
                        print("Error starting VPN Connection \(error.localizedDescription)");
                    }

但是在这一行：

result = try self.vpnManager.connection.startVPNTunnel()

我收到了这个错误：

无法指定类型'（）'的值来输入'Bool？'

Answer 1

文档涉及Objective-C方法。

Objective-C方法-(BOOL)doSomethingAndReturnError:(NSError *...以doSomething() throws的形式向Swift公开。

因此Swift方法没有返回值。你可以简单地写

   do {
       try self.vpnManager.connection.startVPNTunnel()
       NotificationCenter.default.post(name: .enableDisconnect, object: nil)
   } catch {
      print("Error starting VPN Connection \(error.localizedDescription)");
   }

但即使该方法返回Bool在这种情况下从不使用可选项，请使用以下内容：

let result: Bool
do {
   result = try doSomething()    
} catch {
   result = false
   print("Error starting VPN Connection \(error.localizedDescription)");
}
if result {
   NotificationCenter.default.post(name: .enableDisconnect, object: nil)
}

Answer 2

函数startVPNTunnel返回Void。不是Bool。试试这个：

    do {
        try self.vpnManager.connection.startVPNTunnel()

        // If function reached that point startVPNTunnel didn't throw error
    } catch let error {
        // Some error
    }

如何在try catch中分配throwable函数的返回值？

2 个答案: