Cloud.iO Glue

Introduction

This package is an extension to the cloudio-endpoint-python package providing features not present in the java-endpoint implementation. It supports the developer with the Model2CloudConnector class and the 'cloudio_attribute' decorator.

The fast and simple solution to connect an object to the cloud is to inherit the class from CloudioNode and automatically all attributes get synchronized to the cloud. The drawback here is that the developer does not have the choice to prohibit the synchronisation of some attributes.

There is where the Model2CloudConnector class comes in. Inheriting from this class allows specifying which attribute should be synchronized to the cloud using the attribute mapping feature.

Download and Install

The library is available on python's package distribution system PyPi.

From the console you can download and install it using the following command:

   pip install cloudio-glue-python

Model2CloudConnector Class

The Model2CloudConnector class allows to synchronise some attributes of a class. Which attributes to synchronise is done with an attribute mapping.

To use the Model2CloudConnector class you need to inherit from it and then specify which of the attributes to synchronize using the set_attribute_mapping() method.

Attribute Mapping

Here is an example on how to bring attributes (or properties) x and y of the ComputerMouse class to the cloud:

from cloudio.glue import Model2CloudConnector    

class ComputerMouse(Model2CloudConnector):

    def __init__(self):
        super(ComputerMouse, self).__init__()
        self._x = 0
        self._y = 0

        # Define the attributes which are going to be mapped to cloud.iO
        self.set_attribute_mapping({'x': {'topic': 'position.x', 'attributeType': float,
                                          'constraints': ('read',)},  # ('read', 'write')
                                    'y': {'topic': 'position.y', 'attributeType': float,
                                          'constraints': ('read',)},
                                })

    @property
    def x(self): return self._x

    @x.setter
    def x(self, value): self._x = value
    
    @property
    def y(self): return self._y

    @y.setter
    def y(self, value): self._y = value

Attribute Access Policy

For each attribute the access policy can be specified. Following values can be given

• read
• write

or both.

The read access policy allows to read the attribute from the cloud. Giving the write access policy allows to change the attribute via the cloud.

cloudio_attribute Decorator

An attribute can be automatically synchronized to the cloud by assigning the cloudio_attribute decorator to the property.

To assign for example the decorator to the x property change the code above as follows. Remove the @property decorator and replace it with the @cloudio_attribute decorator.

The example below shows the @cloudio_attribute decorator applied to the x and y property:

from cloudio.glue import Model2CloudConnector
from cloudio.glue import cloudio_attribute

class ComputerMouse(Model2CloudConnector):

    def __init__(self):
        super(ComputerMouse, self).__init__()

        self._x = 0
        self._y = 0

        # Define the attributes which are going to be mapped to cloud.iO
        self.set_attribute_mapping({'x': {'topic': 'position.x', 'attributeType': float,
                                          'constraints': ('read',)},  # ('read', 'write')
                                    'y': {'topic': 'position.y', 'attributeType': float,
                                          'constraints': ('read',)},
                                    })

    @cloudio_attribute
    def x(self): return self._x

    @x.setter
    def x(self, value): self._x = value

    @cloudio_attribute
    def y(self): return self._y

    @y.setter
    def y(self, value): self._y = value

Now every time the x or y property gets changed, the value is automatically updated to the cloud.