cloudio-glue-python 1.0.3
cloud.iO endpoint glue
License: MIT
Keywords: cloud.iO endpoint library IoT cloud connector model

# Cloud.iO Glue
![python-version](https://img.shields.io/badge/python-3.x-blue.svg?style=flat)
![version](https://img.shields.io/pypi/v/cloudio-glue-python.svg)
![](docs/images/coverage.svg)


## Introduction
This package is an extension to the 
[cloudio-endpoint-python](https://github.com/cloudio-project/cloudio-endpoint-python) 
package providing features not present in the 
[java-endpoint](https://github.com/cloudio-project/cloudio-endpoint-java)
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](https://pypi.python.org/).

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:

```python
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:

```python
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.