Data.py

'''
This class contains the data for a single Chooser that will be sent to the user.
'''

class DataItem:

    '''
    Creates a DataItem instance (see above description).
    Parameters:
        key - The key to be sent to NetworkTables.
        value - The value to be sent to NetworkTables.
    '''
    def __init__(self, key, value):
        # Set the values that were passed in as parameters.
        self.key = key
        self.value = value

'''
This class contains the data that will be sent to the user.
'''

class Data:

    '''
    Creates a Data instance (see above description).
    '''
    def __init__(self):
        self.dataitems = [] # Create an empty array of DataItems.
        self.observers = [] # Create an empty array of Observers.

    '''
    Adds a DataItem.
    If a DataItem with the same key has already been added, replace the old dataitem with the new one.
    '''
    def addDataItem(self, dataitem):
        # Check if a dataitem with the same key already exists.
        # If it does, set its value to dataitem's value.
        for item in self.dataitems:
            if item.key == dataitem.key:
                item.value = dataitem.value
                return
        # Add the dataitem.
        self.dataitems.append(dataitem)

    '''
    Attaches an Observer.
    '''
    def attach(self, observer):
        if observer not in self.observers:
            self.observers.append(observer)

    '''
    Detaches an Observer.
    '''
    def detach(self, observer):
        self.observers.remove(observer)

    '''
    Notifies all observers of a change.
    Parameter:
        changeditem - The DataItem that was changed.
    '''
    def notify(self, changeditem):
        for observer in self.observers:
            observer.update(changeditem)