設計模式-行為型模式，狀態模式（14）

在狀態模式（State Pattern）中，類的行為是基於它的狀態改變的。這種類型的設計模式屬於行為型模式。

在狀態模式中，我們創建表示各種狀態的對象和一個行為隨着狀態對象改變而改變的 context 對象。

 

class State(object):
    """Base state. This is to share functionality"""

    def scan(self):
        """Scan the dial to the next station"""
        self.pos += 1
        if self.pos == len(self.stations):
            self.pos = 0
        print("Scanning... Station is", self.stations[self.pos], self.name)


class AmState(State):
    def __init__(self, radio):
        self.radio = radio
        self.stations = ["1250", "1380", "1510"]
        self.pos = 0
        self.name = "AM"

    def toggle_amfm(self):
        print("Switching to FM")
        self.radio.state = self.radio.fmstate


class FmState(State):
    def __init__(self, radio):
        self.radio = radio
        self.stations = ["81.3", "89.1", "103.9"]
        self.pos = 0
        self.name = "FM"

    def toggle_amfm(self):
        print("Switching to AM")
        self.radio.state = self.radio.amstate


class Radio(object):
    """A radio.     It has a scan button, and an AM/FM toggle switch."""

    def __init__(self):
        """We have an AM state and an FM state"""
        self.amstate = AmState(self)
        self.fmstate = FmState(self)
        self.state = self.amstate

    def toggle_amfm(self):
        self.state.toggle_amfm()

    def scan(self):
        self.state.scan()


# Test our radio out
if __name__ == '__main__':
    radio = Radio()
    actions = [radio.scan] * 2 + [radio.toggle_amfm] + [radio.scan] * 2
    actions = actions * 2

    for action in actions:
        action()