Difference between revisions of "Phonebot developer's reference/Object reference/Using Phonebot services"

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(Object reference)
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|Retrieve a service property.
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|<code>event = pop_event()</code>
 
|<code>event = pop_event()</code>
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|<code>start()</code>
 
|<code>start()</code>

Revision as of 23:50, 27 March 2012

Services are non-visual components that monitor different environment states and trigger an event when the state changes. The available services are:

  • http - Make web requests
  • sensor - Monitor hardware sensors
  • timer - Alert at specific intervals

When a service is updated, its OnUpdate event fires, then the application's OnService event fires, and finally the current module's OnService event fires.

Each Service stores its update data in a queue. The methods get_event() and pop_event() access the next event in the queue and event_size returns how many events exist.

The maximum number of sensor events that will be retained in the queue is controlled by the "Sensor buffer" Phonebot property. The "Sensor buffer" value, the sensor service's "Minimum update frequency" value, and the amount of script within each OnUpdate and OnService event will determine how responsive your application is when reading sensor data. If updates are sluggish, try reducing the buffer size.

Service lifecycle

A service's properties, methods, and the application state affect that service's lifetime as the following diagram illustrates:

Phonebot.service-lifecycle.png

A service will start running:

  • When its start() method is called
  • If its autostart property is set to true, immediately after the application starts

A service will stop running:

  • When its stop() method is called
  • If its system property is set to false, when the application loses focus
  • If its system property is set to true, when the application exits

Object reference

Properties

Syntax Description
auto_start Read-only boolean. Set to true to start the service as soon as the application starts.
event_size Read-only. The number of events in the queue. When monitoring multiple services, this property can be used in on_service events to determine which service was updated.
name Read-only.
system Read-only boolean. Set to true to have the service run even when the application has lost focus.
text Read-only.

Methods

Syntax Description
size = clear_events() Delete all events and return how many were deleted.
event = get_event() Retrieve the next event in the queue.
value = get_property(name) Retrieve the value of a custom property (see below).
event = pop_event() Retrieve and delete the next event in the queue.
set_property(name, value) Set the value of a custom property (see below).
start() Start the service.
stop() Stop the service.

Events

Syntax Description
on_service

In addition to the common properties, methods, and events, each service may have custom properties accessible from the get_property() and set_property() methods:

Service Properties Description
http url Makes a GET request to a URL. Returns a single event in the queue containing the response.
sensor sensors - array of sensor names

update_frequency - time between updates in milliseconds

Monitors one or more hardware sensors. Returns an event containing a comma-delimited list of values beginning with the sensor name (e.g. orientation,60.0,-28.0,3.0). The range of each value is dependent on the sensor.
timer duration - time between updates, formatted as h:m:s, m:s, or s Fire the update events at regular intervals. The event will first fire immediately after the service is started. Returns an event containing the datetime value when the update happened.

Events can be accessed and parsed in the following manner:

HTTP:

event = http_service.pop_event()
// query with XPath
items = event:xml.query("//root/item")
// read json data
root = event:json.get_element("root")
items = event:json.get_element("item")

Sensor:

event = sensor_service.pop_event()
event = event:string.split(",")
name = event:array.get_element(0)
// get values from index 1 and greater

Timer:

event = timer_service.pop_event()
event = event:datetime.format("HH:mm:ss")

The sensor service can be configured to return any combination of sensor types. Each type has its own name and data format as described below:

Name Structure of event value

(actual values are prefixed with the name, i.e. name,value1,value2,...)

Description
accelerometer x,y,z Acceleration in meters/second^2
gps latitude,longitude,accuracy,altitude,bearing,speed
gravity x,y,z Gravity in meters/second^2
gyroscope x,y,z Angular speed in radian/second
light l Ambient light in lux units
linear_acceleration Acceleration in meters/second^2
magnetic_field x,y,z Magnetic field in micro-Teslas
orientation azimuth,pitch,roll Measured in degrees. 0=North, 90=East, 180=South, 270=West; -180..180; -90..90
pressure p Atmospheric pressure in millibars
proximity p Proximity in centimeters
rotation_vector
temperature

--SensorEvent values