Created
June 7, 2020 10:39
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Use factory method to create objects based on description (str/dict).
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| """ | |
| """ | |
| from abc import ABC, abstractmethod | |
| from functools import lru_cache | |
| from collections.abc import Set, Mapping | |
| class Task(ABC): | |
| def __init__(self, context): | |
| self.context = context | |
| @classmethod | |
| @lru_cache(maxsize=None) | |
| def get_subclasses(cls): | |
| """ | |
| """ | |
| subclasses = [] | |
| for subclass in cls.__subclasses__(): | |
| subclasses.append(subclass) | |
| subclasses.extend(subclass.get_subclasses()) | |
| return subclasses | |
| @classmethod | |
| def factory(cls, context, task_description): | |
| for task_type in cls.get_subclasses(): | |
| if isinstance(task_description, str) and isinstance(task_type.description, str): | |
| if task_description == task_type.description: | |
| return task_type(context) | |
| elif isinstance(task_description, Mapping) and isinstance(task_type.description, Set): | |
| if task_description.keys() >= task_type.description: | |
| return task_type(context, **task_description) | |
| else: | |
| raise Exception("invalid task description: {task_description}") | |
| def __repr__(self): | |
| return f"<Task: {self.description}>" | |
| @abstractmethod | |
| def run(self): | |
| pass | |
| class ShutdownTask(Task): | |
| description = "shutdown" | |
| def run(self): | |
| pass | |
| class CloneTask(Task): | |
| description = {"clone", "target"} | |
| def __init__(self, context, clone, target, **kwargs): | |
| super().__init__(context) | |
| self.clone = clone | |
| self.target = target | |
| def __repr__(self): | |
| return f"<Task: clone({self.clone}) target({self.target})>" | |
| def run(self): | |
| pass | |
| class InstallTask(Task): | |
| description = {"install"} | |
| def __init__(self, context, install, **kwargs): | |
| super().__init__(context) | |
| self.install = install | |
| def __repr__(self): | |
| return f"<Task: install({self.install})>" | |
| def run(self): | |
| pass | |
| class DryRunVirtualMachine: | |
| def __init__(self, name): | |
| self.name = name | |
| def __repr__(self): | |
| return f"<DryRunVirtualMachine {self.name}>" | |
| class Context: | |
| pass | |
| if __name__ == "__main__": | |
| TASKS = [ | |
| { | |
| "install": "test", | |
| "bla": 5, | |
| }, | |
| "shutdown", | |
| { | |
| "clone": "test", | |
| "target": "test2", | |
| }, | |
| { | |
| "install": "test", | |
| "bla": 5, | |
| }, | |
| ] | |
| context = Context() | |
| context.vm = DryRunVirtualMachine("BLA") # dry_run | |
| for n, task_description in enumerate(TASKS): | |
| task = Task.factory(context, task_description) | |
| print(n, task) |
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