modo channel reading API

channelRead.py

#  @author David Ballesteros
#
#  @brief Helper classes to deal with the read and write of Item Channels.
#         Based on a ChannelRead class sample code provided by Matt Cox

import lx

class ChannelRead:
    def __init__(self, item):
        """
        Class to read channel values and action layers at certain time
        :param self
        :param item The Item from which read a Channel value.
        :return: None
        :rtype: None
        """
        
        # Get the selection service
        self.sel_svc = lx.service.Selection()
        
        # Get a new ChannelRead object
        self.chan_read_obj = lx.object.ChannelRead()
        
        # Keep the passed Item
        self.item = lx.object.Item(item)
        
        # Get the Scene the Item belongs to
        self.scene = self.item.Context()
        
        # Set the Action layer. EDIT by default
        self.action_layer = lx.symbol.s_ACTIONLAYER_EDIT
        
        # Assign the ChannelRead object at the actual time
        # scene.Channels() can create a ChannelRead Object or a ChannelWrite Object
        # In Python always return a ChannelRead Object unless you cast it
        self.chan_read_obj = self.scene.Channels (self.action_layer, self.sel_svc.GetTime())
    
    def AtTime(self, time):
        """ Obtains the ChannelRead object at certain time """
        # @param time float - The time at which obtain the ChannelRead object.        
        
        self.chan_read_obj = self.scene.Channels (self.action_layer, time)
    
    def FromEdit(self):
        """ Obtains the ChannelRead object from the Edit Action Layer at the actual time """
        self.action_layer = lx.symbol.s_ACTIONLAYER_EDIT
        self.chan_read_obj = self.scene.Channels (self.action_layer, self.sel_svc.GetTime())

    def FromSetup(self):
        """ Obtains the ChannelRead object from the Setup Action Layer at the actual time """
        self.action_layer = lx.symbol.s_ACTIONLAYER_SETUP
        self.chan_read_obj = self.scene.Channels (self.action_layer, self.sel_svc.GetTime())
    
    def GetValue (self, channel):
        """ Read the value of a channel by name """
        # @param channel String - The name of the Channel to get it's value.        

        channel_id = None
        # Check is passed a string with the name of a channel
        if isinstance(channel, str):
            channel_id = self.item.ChannelLookup(channel)
        
        # Get the Channel type   
        chan_type = self.item.ChannelEvalType(channel_id)

        # Return the appropiate value depending on the Channel Type        
        if chan_type == "float":
            return self.chan_read_obj.Double(self.item, channel_id)
    
        if chan_type == "integer":
            return self.chan_read_obj.Integer(self.item, channel_id)
        
        if chan_type == "string":
            return self.chan_read_obj.String(self.item, channel_id)
        
    def GetValueAtTime (self, channel, key = 0.0):
        """ Read the value of a channel by name """
        # @param channel String - The name of the Channel to get it's value.        

        channel_id = None
        # Check is passed a string with the name of a channel
        if isinstance(channel, str):
            channel_id = self.item.ChannelLookup(channel)
        
        # Get the Channel type   
        chan_type = self.item.ChannelEvalType(channel_id)

        # Return the appropiate value depending on the Channel Type        
        if chan_type == "float":
            return self.chan_read_obj.Double(self.item, channel_id)
    
        if chan_type == "integer":
            return self.chan_read_obj.Integer(self.item, channel_id)
        
        if chan_type == "string":
            return self.chan_read_obj.String(self.item, channel_id)        
        
class ChannelWrite:
    def __init__(self, item):
        """ Class to write channel values and action layers at certain time"""
        # @param item Item - The Item from wich read a Channel value.                
        
        # Get the selection service
        self.sel_svc = lx.service.Selection()
        
        # Get a new ChannelWrite object
        self.chan_write_obj = lx.object.ChannelWrite()
        
        # Keep the passed Item
        self.item = lx.object.Item(item)
        
        # Get the Scene the Item belongs to
        self.scene = self.item.Context()
        
        # Set the Action layer. EDIT by default
        self.action_layer = lx.symbol.s_ACTIONLAYER_EDIT
        
        # Assing the ChannelRead object at the actual time
        # scene.Channels() can create a ChannelRead Object or a ChannelWrite Object
        # In Python always return a ChannelRead Object unles you cast it
        self.chan_write_obj = lx.object.ChannelWrite(self.scene.Channels (self.action_layer, self.sel_svc.GetTime()))
      
    def AtTime(self, time):
        """ Obtains the ChannelWrite object at certain time """
        # @param time float - The time at which obtain the ChannelWrite object.          
        self.chan_write_obj = lx.object.ChannelWrite(self.scene.Channels (self.action_layer, time))

    def FromEdit(self):
        """ Obtains the ChannelWrite object from the Edit Action Layer at the actual time """
        self.action_layer = lx.symbol.s_ACTIONLAYER_EDIT
        self.chan_write_obj = lx.object.ChannelWrite(self.scene.Channels (self.action_layer, self.sel_svc.GetTime()))

    def FromSetup(self):
        """ Obtains the ChannelWrite object from the Setup Action Layer at the actual time"""
        self.action_layer = lx.symbol.s_ACTIONLAYER_SETUP
        self.chan_write_obj = lx.object.ChannelWrite(self.scene.Channels (self.action_layer, self.sel_svc.GetTime()))
    
    def SetValue (self, channel, value):
        """
        Write the value of a channel by name

        :param channel: The name of the Channel to set it's value.
        :type channel: string

        """

        channel_id = None
        # Check is passed a string with the name of a channel
        if isinstance(channel, str):
            channel_id = self.item.ChannelLookup(channel)
        
        # Get the Channel type
        chan_type = self.item.ChannelEvalType(channel_id)
    
        # Write the appropriate value depending on the Channel Type
        
        if chan_type == "float":
            self.chan_write_obj.Double(self.item, channel_id, value)
    
        if chan_type == "integer":
            self.chan_write_obj.Integer(self.item, channel_id, value)
        
        if chan_type == "string":
            self.chan_write_obj.String(self.item, channel_id, value)