Template Method - 模板方法模式

void Application::openDocument(const char* name)
{
    if(!canOpenDocument(name))
        return;
    
    Document* doc = createDocument();
    if(doc != NULL)
    {
        m_docs->addDocument(doc);
        aboutToOpenDocument(doc);
        doc->open();
        doc->read();
    }
}

class Application
{
public:
    void openDocument(const char* name);
protected:
    virtual void canOpenDocument(const char* name);
    virtual void createDocument();
    virtual void aboutToOpenDocument();
private:
    vector<Document*> m_docs;
};

class MyApplication : public Application
{
protected:
    virtual Document* createDocument();
    virtual void aboutToOpenDocument();
};
Document* MyApplication::createDocument()
{
   return new MyDocument();
}
void aboutToOpenDocument()
{
    // initialize doc object.
}