Adapter Pattern
Published:
Adapter 接的東西是什麼?
- 插座 (台灣) <—- adapter (轉接器) —-> 電器 (中國)
- 不會為了中國電器 在牆上做一個插頭
- 也不會為了 台灣插座，改中國的電器
- 筆電 <—- adapter (外接器) —-> 網絡線
- 不會為了網路線在筆電上挖網絡孔
- 也不會去變更網絡線的連線方式去適配筆電現有的接口
point: 插頭 / 電腦
Scenario
It’s very often used in systems based on some legacy code. In such cases, Adapters make legacy code work with modern classes.
- legacy systems (mysql)
- magic interface (input: json format)
Case Study
class MacBook {
public:
virtual HDMI::DataType HDMIPort() const {
return "HDMI signal";
}
};
class Monitor {
public:
void VGAPortDisplay(VGA::DataType data) const {
std::cout << "Displaying on Monitor: " << data << std::endl;
}
};
class Adapter : public MacBook {
private:
Monitor *monitor_;
public:
Adapter(Monitor *monitor) : monitor_(monitor) {}
VGA::DataType HDMI2VGA(HDMI::DataType data) const {
return "Converted to VGA: " + data;
}
HDMI::DataType HDMIPort() const override {
VGA::DataType vgaData = HDMI2VGA("HDMI signal from MacBook");
monitor_->VGAPortDisplay(vgaData);
return "HDMI signal handled by VGA monitor";
}
};