Proof of concept for an undo and redo function using python functions. This is for use in the pyrrhic-ree project. By using properties it is possible to build the undo stack just by setting the string. Once a stack is built calling the undo function builds a redo stack that is emptied once a person decides to type manually. I don't think there i…

undo-redo-proof.py

class Proof:
    def __init__(self):
        self._redo = []
        self._undo = []
        self._mystr = ''

    def mystr():
        def fget(self):
            return self._mystr

        def fset(self, value):
            self._undo.append(self.buildStrRevert())
            self._redo = []  # empty redo ability when string is set
            self._mystr = value
        return locals()
    mystr = property(**mystr())

    def undo(self):
        if self._undo:
            self._redo.append(self.buildStrRevert())
            self._undo.pop()()

    def redo(self):
        if self._redo:
            self._undo.append(self.buildStrRevert())
            self._redo.pop()()

    def myostr():
        def fget(self):
            return self._myostr

        def fset(self, value):
            self._undo.append(self.buildStrRevert())
            self._redo = []  # empty redo ability when string is set
            self._myostr = value
        return locals()
    myostr = property(**myostr())

    #builds a function that will use a closure
-   #to save and revert the strings in one simple action
    #The closure maintains the state before the change.
    #It would be possible to build a more complex system using
    #multiple function wrappers, but this allows for a uniform
    #interface with only 2 stacks.
    def buildStrRevert(self):
        oldMyStr = self._mystr
        oldMyOStr = self._myostr

        def strRevert():
            self._mystr = oldMyStr
            self._myostr = oldMyOStr
        return strRevert