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January 21, 2014 04:47
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GoF design pattern with Python. - Strategy
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# http://stackoverflow.com/questions/963965/how-is-this-strategy-pattern | |
# -written-in-python-the-sample-in-wikipedia | |
""" | |
In most of other languages Strategy pattern is implemented via creating some | |
base strategy interface/abstract class and subclassing it with a number of | |
concrete strategies (as we can see at | |
http://en.wikipedia.org/wiki/Strategy_pattern), however Python supports | |
higher-order functions and allows us to have only one class and inject | |
functions into it's instances, as shown in this example. | |
""" | |
import types | |
class StrategyExample: | |
def __init__(self, func=None): | |
self.name = 'Strategy Example 0' | |
if func is not None: | |
self.execute = types.MethodType(func, self) | |
def execute(self): | |
print(self.name) | |
def execute_replacement1(self): | |
print(self.name + 'from execute 1') | |
def execute_replacement2(self): | |
print(self.name + 'from execute 2') | |
if __name__ == '__main__': | |
strat0 = StrategyExample() | |
strat1 = StrategyExample(execute_replacement1) | |
strat1.name = 'Strategy Example 1' | |
strat2 = StrategyExample(execute_replacement2) | |
strat2.name = 'Strategy Example 2' | |
strat0.execute() | |
strat1.execute() | |
strat2.execute() | |
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