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Question

有没有办法在Swift的运行时设置扩展名？

我得到了一个名为＆＃34; CuteProtocol＆＃34;该协议的扩展名为＆＃34; CuteExtension＆＃34;。当我想将这个扩展添加到类时，我只需按以下步骤操作：

class CuteClass: UIViewController, CuteProtocol {

}

但是我有很多这样的课程应该实现这个协议，我不想一个一个地添加它们，我也不想创建基类。

有没有办法在运行时设置扩展协议，如下所示：

let cuteClass = CuteClass()
cuteClass. // ADD EXTENSION-PROTOCOL SOMEHOW HERE.

Answer 1

不，但你可以扩展例如UIViewController或其他基类

11/01/17 12:16:15] [SSH] Opening SSH connection to 192.168.226.197:22.
/var/lib/jenkins/.ssh/known_hosts [SSH] No Known Hosts file was found at /var/lib/jenkins/.ssh/known_hosts. Please ensure one is created at this path and that Jenkins can read it.
Key exchange was not finished, connection is closed.
java.io.IOException: There was a problem while connecting to 192.168.226.197:22
    at com.trilead.ssh2.Connection.connect(Connection.java:834)
    at com.trilead.ssh2.Connection.connect(Connection.java:703)
    at com.trilead.ssh2.Connection.connect(Connection.java:617)
    at hudson.plugins.sshslaves.SSHLauncher.openConnection(SSHLauncher.java:1284)
    at hudson.plugins.sshslaves.SSHLauncher$2.call(SSHLauncher.java:804)
    at hudson.plugins.sshslaves.SSHLauncher$2.call(SSHLauncher.java:793)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.io.IOException: Key exchange was not finished, connection is closed.
    at com.trilead.ssh2.transport.KexManager.getOrWaitForConnectionInfo(KexManager.java:95)
    at com.trilead.ssh2.transport.TransportManager.getConnectionInfo(TransportManager.java:237)
    at com.trilead.ssh2.Connection.connect(Connection.java:786)
    ... 9 more
Caused by: java.io.IOException: The server hostkey was not accepted by the verifier callback
    at com.trilead.ssh2.transport.KexManager.handleMessage(KexManager.java:548)
    at com.trilead.ssh2.transport.TransportManager.receiveLoop(TransportManager.java:790)
    at com.trilead.ssh2.transport.TransportManager$1.run(TransportManager.java:502)
    ... 1 more
[11/01/17 12:16:15] Launch failed - cleaning up connection
[11/01/17 12:16:15] [SSH] Connection closed.

Answer 2

你可以自由地在 ObjC 中使用运行时修饰符，但在 Swift 中，这种有点模式并不常见。

注意： 如果您有兴趣，可以在ObjC Runtime Library找到有关此内容的更多信息。

Answer 3

您无法在运行时设置扩展名，但您也不必在类定义中设置它们。你可以扩展类：

extension CuteClass: CuteProtocol {
    // your code conforming to Cute Protocol goes here.
}

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或者，如果您希望将默认实施设置为CuteProtocol，您也可以自己扩展CuteProtocol：

protocol CuteProtocol {
    func f1()
}

extension CuteProtocol {
    func f1() {
        // default implementation
    }
}

这样，如果想要或使用默认实现，每个类都可以更改f1实现。

您甚至可以添加条件扩展名，如：

extension CuteProtocol where Self: CuteClass {
    func f1() { }
    func f2() { }
}

所以如果你写extension CuteClass: CuteProtocol {}，所有CuteClass实例和子类都可以访问方法f1和f2。

但请注意，扩展中添加的功能支持在protocol中定义的动态调度IFF。在我提供的示例中，将使用动态分派调用f1，但将使用静态分派调用f2。即：如果CuteChildClass: CuteClass更改f2实施，并且您从f2变量调用CuteProtocol，则会调用您在扩展程序中提供的代码。

Swift Advanced - 在运行时设置扩展

3 个答案:

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