组合对象如何引用它内部组成的对象

Question

我的应用程序中有以下类。

class Command: 
    def __init__(self, command_id, command_name, exec_string):
        self.command_name = command_name
        self.exec_string = exec_string
class Checkpoint:
    def __init__(self, checkpoint_id, checkpoint_name, commands):
        self.checkpoint_id = checkpoint_id
        self.checkpoint_name = checkpoint_name
        self.commands = commands
class Job:
    def __init__(self, job_id, job_name, checkpoints):
        self.job_id = job_id
        self.job_name = job_name
        self.checkpoints = checkpoints

我也有执行器类，如下所示

class JobExecutor:
    def __init__(self, checkpoint_executor):
        self.checkpoint_executor = checkpoint_executor
    def execute_job(self, job):
        # set job state to running
        # run job
        for checkpoint in job.checkpoints:
            self.checkpoint_executor.execute_checkpoint(checkpoint)
class CheckpointExecutor:
    def __init__(self, command_executor):
        self.command_executor = command_executor
    def execute_checkpoint(self, checkpoint):
        # set checkpoint state to running
        # run checkpoint
        for command in checkpoint.commands:
            self.command_executor.execute_command(command)
class CommandExecutor:
    def run_process(self, exe): 
        import subprocess
        try:
            p = subprocess.Popen(exe, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
            stdout,stderr = p.communicate()
            return stdout
        except FileNotFoundError as error:
            pass
    def execute_command(self, command):
        # set command state to running
        # run command
        output = run_process(command.exec_string.split()))
        if output:
            # set command state to completed
        else:
            # set command state to failed

示例用法

command1 = Command(command_id = 1 , command_name = "echo", exec_string = "echo start")
command2 = Command(command_id = 2 , command_name = "list", exec_string = "ls -i")
command3 = Command(command_id = 3 , command_name = "wordcount", exec_string = "wc -l Decorator.ipynb")
checkpoint1 = Checkpoint(checkpoint_id = 1, checkpoint_name = "first_checkpoint", commands = [command1, command2])
checkpoint2 = Checkpoint(checkpoint_id = 2, checkpoint_name = "second_checkpoint", commands = [command3])
job = Job(job_id = 1, job_name = "unix tutorial", checkpoints = [checkpoint1, checkpoint2])
job_executor = JobExecutor(CheckpointExecutor(CommandExecutor()))
job_executor.execute_job(job)

在"execute_checkpoint"方法中，我想引用包含此检查点的作业对象，而在"execute_command"方法中，我想引用包含此命令的检查点对象。如何在不损坏执行方法签名的情况下做到这一点？

Answer 1

如何"引用包含此检查点的作业对象">

您可以添加一个字段来引用父字段，并在创建作业时分配给该字段。

class Checkpoint:
    def __init__(self, checkpoint_id, checkpoint_name, commands):
        self.checkpoint_id = checkpoint_id
        self.checkpoint_name = checkpoint_name
        self.commands = commands
        self.parent = None                           # <== Placeholder          
class Job:
    def __init__(self, job_id, job_name, checkpoints):
        self.job_id = job_id
        self.job_name = job_name
        self.checkpoints = checkpoints
        for checkpoint in checkpoints:               # <== All checkpoints   
            checkpoint.parent = self                 # <== Store ref to parent