# validated: 2024-01-24 DS 192a28af4731 DeferredCommand.java
from typing import Callable
from wpiutil import SendableBuilder
from .command import Command
from .commandscheduler import CommandScheduler
from .printcommand import PrintCommand
from .subsystem import Subsystem
[docs]
class DeferredCommand(Command):
"""
Defers Command construction to runtime. Runs the command returned by a supplier when this command
is initialized, and ends when it ends. Useful for performing runtime tasks before creating a new
command. If this command is interrupted, it will cancel the command.
Note that the supplier *must* create a new Command each call. For selecting one of a
preallocated set of commands, use :class:`commands2.SelectCommand`.
"""
def __init__(self, supplier: Callable[[], Command], *requirements: Subsystem):
"""
Creates a new DeferredCommand that directly runs the supplied command when initialized, and
ends when it ends. Useful for lazily creating commands when the DeferredCommand is initialized,
such as if the supplied command depends on runtime state. The Supplier will be called
each time this command is initialized. The Supplier *must* create a new Command each call.
:param supplier: The command supplier
:param requirements: The command requirements.
"""
super().__init__()
assert callable(supplier)
self._null_command = PrintCommand(
f"[DeferredCommand] Supplied command (from {supplier!r} was None!"
)
self._supplier = supplier
self._command = self._null_command
self.addRequirements(*requirements)
[docs]
def initialize(self):
cmd = self._supplier()
if cmd is not None:
self._command = cmd
CommandScheduler.getInstance().registerComposedCommands([self._command])
self._command.initialize()
[docs]
def execute(self):
self._command.execute()
[docs]
def isFinished(self):
return self._command.isFinished()
[docs]
def end(self, interrupted):
self._command.end(interrupted)
self._command = self._null_command
[docs]
def initSendable(self, builder: SendableBuilder):
super().initSendable(builder)
builder.addStringProperty(
"deferred",
lambda: (
"null"
if self._command is self._null_command
else self._command.getName()
),
lambda _: None,
)