Question

我需要向对象添加其他数据 - 但我不需要添加功能。因此以下是经典GOF装饰模式的一个例子？

class ClassIWantToDecorate
{
    public string GetData() { return "data"; }
}

class Decorator
{
    private ClassIWantToDecorate _classIWantToDecInstance = null;
    private string _additionalData;
    public Decorator(ClassIWantToDecorate classIWantToDec, string additionalData)
    {
        _classIWantToDecInstance = classIWantToDec;
        _additionalData = additionalData;
    }

    public string DataINeed()
    {
        return _classIWantToDecInstance.GetData();
    }

    public string AdditionalDataINeed()
    {
        return _additionalData;
    }
}

Answer 1

没有。我会说它只是composition。

装饰师会是这样的：

interface DataINeedProvider {
    string DataINeed();
}

class LoggingDecorator implements DataINeedProvider
{
    private DataINeedProvider _classIWantToDecInstance = null;
    private Logger logger = new Logger();
    public LoggingDecorator(DataINeedProvider classIWantToDec) {
        _classIWantToDecInstance = classIWantToDec;
    }

    public string DataINeed()
    {
        logger.log("DataINeed has been called");
        return _classIWantToDecInstance.DataINeed();
    }
}

PS：对不起，如果这是无效的C＃语法。我是一名Java开发人员。

Answer 2

您的实现问题是您的装饰器界面与装饰对象的界面不兼容。

有效的装饰解决方案是：

interface ClassIWantToDecorateInterface {
  public string GetData();
}

class ClassIWantToDecorate implements ClassIWantToDecorateInterface {
    public string GetData() { return "data"; }
}

class Decorator implements ClassIWantToDecorateInterface {
    private ClassIWantToDecorateInterface _classIWantToDecInstance = null;
    private string _additionalData;
    public Decorator(ClassIWantToDecorateInterface classIWantToDec, string additionalData)
    {
        _classIWantToDecInstance = classIWantToDec;
        _additionalData = additionalData;
    }

    public string GetData() {
        return _classIWantToDecInstance.GetData();
    }

    public string AdditionalDataINeed() {
        return _additionalData;
    }
}

（我使用java语法，因为我不确定你是使用C＃还是Java。根据语法，它可能都是）

这是装饰器模式的一个例子（向对象添加数据）吗？

2 个答案: