SP1 - Adapter - Learn Design Pattern From Simple Things

Adapter is a structural design pattern: 🖤🖤🖤🖤🖤

What is Adapter?

Adapter is a set of converters(USB-B to USB-C, USB-A to USB-C, HDMI to USB-C).

Adapter makes it possible for the main device (Macbook) to be connected to incompatible devices (<Printer>, <Flash>, <Monitor>)

Adapter diagram

Why use Adapter?

It’s all in one converter, neat and clean

Use Adapter: USB type C Adapter

Question: I hate the Adapter, what are the alternatives?

Answer: You can buy separate converters(USB type B to type C cable, USB type A to type C cable, HDMI to type C cable) for replacement!

Use Many Converters: Many Separate Converters

When to use Adapter?

Question: When I need a USB type C Adapter?

Answer: When you need to connect Printer, Flash or Monitor to Macbook, right?

Input:

Having a Macbook, that only have the USB type C port.
Having incompatible (non-USB type C) devices:
- Printer (USB type B)
- Flash (USB type A)
- Monitor (HDMI)

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# Input 2: Having incompatible (non-USB type C) devices:
class Printer:
    name = "Printer"

    def connect_usb_b(self):
        return f"{self.name} is connected: Printing..."


# Input 2: Having incompatible (non-USB type C) devices:
class Flash:
    name = "Flash"

    def connect_usb_a(self):
        return f"{self.name} is connected: Copying..."


# Input 2: Having incompatible (non-USB type C) devices:
class Monitor:
    name = "Monitor"

    def connect_hdmi(self):
        return f"{self.name} is connected: Displaying..."

Expected Output:

Making that non-USB type C devices have USB type C port
- Printer (USB type C)
- Flash (USB type C)
- Monitor (USB type C)
MacBook is able to connect to those incompatible devices

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Printer is connected: Printing...
Flash is connected: Copying...
Monitor is connected: Displaying...

How to implement Adapter?

Non-Adapter implementation:

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if __name__ == "__main__":
    devices = [Printer(), Flash(), Monitor()]
    for device in devices:
        if isinstance(device, Printer):
            # Expected Output 2: MacBook is able to connect to those incompatible devices
            print(device.connect_usb_b())
        elif isinstance(device, Flash):
            # Expected Output 2: MacBook is able to connect to those incompatible devices
            print(device.connect_usb_a())
        elif isinstance(device, Monitor):
            # Expected Output 2: MacBook is able to connect to those incompatible devices
            print(device.connect_hdmi())

Adapter Implementation:

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class Adapter:
    def __init__(self, obj, **adapted_methods):
        self.obj = obj
        self.__dict__.update(adapted_methods)

    def __getattr__(self, attr):
        return getattr(self.obj, attr)


if __name__ == "__main__":
    devices = []
    printer = Printer()
    # Expected Output 1: Making that non-USB type C devices have USB type C port
    devices.append(Adapter(printer, connect=printer.connect_usb_b))
    flash = Flash()
    # Expected Output 1: Making that non-USB type C devices have USB type C port
    devices.append(Adapter(flash, connect=flash.connect_usb_a))
    monitor = Monitor()
    # Expected Output 1: Making that non-USB type C devices have USB type C port
    devices.append(Adapter(monitor, connect=monitor.connect_hdmi))
    for device in devices:
        # Expected Output 2: MacBook is able to connect to those incompatible devices
        print(device.connect())

Source Code