Required Setup or Teardown Code

If, after the use of a class or method, several lines of code are required to:

• set it properly up,
• the environment requires specific actions beforehand or after its use,
• clean up actions are required,

then there is a Required Setup or Teardown Code code smell. Furthermore, this may indicate improper abstraction level.

Causation

Some functionality was taken beyond the class during development, and the need for their use within the class itself was overlooked.

Problems

Lack of Cohesion

Class can't be reused by itself - it requires extra lines of code outside of its scope to use it.

Examples

class Radio:
    def __init__(self, ip, port):
        socket = socket.connection(f"{ip}:{port}")

    ...

radio: Radio = Radio(ip, port)
...
# Doing something with the object
...
# Finalizing its use
radio.socket.shutdown(socket.shut_RDWR)
radio.socket.close()
...

class Radio:
    def __init__(self, ip, port):
        socket = socket.connection(f"{ip}:{port}")

    def __del__(self):
        def graceful_shutdown():
            self.socket.shutdown(socket.shut_RDWR)
            self.socket.close()

        graceful_shutdown()
        super().__del__()

    ...

radio: Radio = Radio(ip, port)
...
# Doing something with the object
...
# Finalizing its use no longer requires manual socket closing
...

Refactoring:

• Replace Constructor with Factory Method
• Introduce Parameter Object

Sources

• [Origin] - Steve Smith, "Refactoring Fundamentals" (2013)