A single snapshot is useful, but a real editor keeps a whole history. The caretaker (the part that manages saved snapshots) lives right inside the Editor as a list used like a stack.
The list _history is already created for you in init. Implement two methods:
Because a stack is last in, first out, calling undo repeatedly walks backward through your edits in reverse order. The typical flow is: call backup before you make a change, then undo to step back to the snapshot you took.
class Memento:
def __init__(self, state):
self._state = state
def get_state(self):
return self._state
class Editor:
def __init__(self):
self.content = ""
self._history = []
def save(self):
return Memento(self.content)
def restore(self, memento):
self.content = memento.get_state()
def backup(self):
"""Push a snapshot of the current content onto the undo stack."""
# TODO: append self.save() to self._history
pass
def undo(self):
"""Pop the most recent snapshot and restore it (no-op if empty)."""
# TODO: if history is non-empty, pop the last memento and restore it
pass
The editor and the test runner need a wide screen. Open this page on a desktop browser and your progress will be waiting.
A single snapshot is useful, but a real editor keeps a whole history. The caretaker (the part that manages saved snapshots) lives right inside the Editor as a list used like a stack.
The list _history is already created for you in init. Implement two methods:
Because a stack is last in, first out, calling undo repeatedly walks backward through your edits in reverse order. The typical flow is: call backup before you make a change, then undo to step back to the snapshot you took.
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