State Patterns

Author: MilovanTomasevic

src/1_patterns/4_BehavioralPatterns/8_State/1_classic.py

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+# interesting but not practical :)
+from abc import ABC
+
+
+class Switch:
+    def __init__(self):
+        self.state = OffState()
+
+    def on(self):
+        self.state.on(self)
+
+    def off(self):
+        self.state.off(self)
+
+
+class State(ABC):
+    def on(self, switch):
+        print('Light is already on')
+
+    def off(self, switch):
+        print('Light is already off')
+
+
+class OnState(State):
+    def __init__(self):
+        print('Light turned on')
+
+    def off(self, switch):
+        print('Turning light off...')
+        switch.state = OffState()
+
+
+class OffState(State):
+    def __init__(self):
+        print('Light turned off')
+
+    def on(self, switch):
+        print('Turning light on...')
+        switch.state = OnState()
+
+
+if __name__ == '__main__':
+    sw = Switch()
+
+    sw.on()  # Turning light on...
+             # Light turned on
+
+    sw.off()  # Turning light off...
+              # Light turned off
+
+    sw.off()  # Light is already off
+
+

src/1_patterns/4_BehavioralPatterns/8_State/2_handmade.py

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+from enum import Enum, auto
+
+
+class State(Enum):
+    OFF_HOOK = auto()
+    CONNECTING = auto()
+    CONNECTED = auto()
+    ON_HOLD = auto()
+    ON_HOOK = auto()
+
+
+class Trigger(Enum):
+    CALL_DIALED = auto()
+    HUNG_UP = auto()
+    CALL_CONNECTED = auto()
+    PLACED_ON_HOLD = auto()
+    TAKEN_OFF_HOLD = auto()
+    LEFT_MESSAGE = auto()
+
+
+if __name__ == '__main__':
+    rules = {
+        State.OFF_HOOK: [
+            (Trigger.CALL_DIALED, State.CONNECTING)
+        ],
+        State.CONNECTING: [
+            (Trigger.HUNG_UP, State.ON_HOOK),
+            (Trigger.CALL_CONNECTED, State.CONNECTED)
+        ],
+        State.CONNECTED: [
+            (Trigger.LEFT_MESSAGE, State.ON_HOOK),
+            (Trigger.HUNG_UP, State.ON_HOOK),
+            (Trigger.PLACED_ON_HOLD, State.ON_HOLD)
+        ],
+        State.ON_HOLD: [
+            (Trigger.TAKEN_OFF_HOLD, State.CONNECTED),
+            (Trigger.HUNG_UP, State.ON_HOOK)
+        ]
+    }
+
+    state = State.OFF_HOOK
+    exit_state = State.ON_HOOK
+
+    while state != exit_state:
+        print(f'The phone is currently {state}')
+
+        for i in range(len(rules[state])):
+            t = rules[state][i][0]
+            print(f'{i}: {t}')
+
+        idx = int(input('Select a trigger:'))
+        s = rules[state][idx][1]
+        state = s
+
+    print('We are done using the phone.')

src/1_patterns/4_BehavioralPatterns/8_State/3_switch_based.py

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+from enum import Enum, auto
+
+
+class State(Enum):
+    LOCKED = auto()
+    FAILED = auto()
+    UNLOCKED = auto()
+
+
+if __name__ == '__main__':
+    code = '1234'
+    state = State.LOCKED
+    entry = ''
+
+    while True:
+        if state == State.LOCKED:
+            entry += input(entry)
+
+            if entry == code:
+                state = State.UNLOCKED
+
+            if not code.startswith(entry):
+                # the code is wrong
+                state = State.FAILED
+        elif state == State.FAILED:
+            print('\nFAILED')
+            entry = ''
+            state = State.LOCKED
+        elif state == State.UNLOCKED:
+            print('\nUNLOCKED')
+            break