add_callback

glue.external.echo.add_callback(instance, prop, callback, echo_old=False, priority=0)[source]

Attach a callback function to a property in an instance

Parameters
instance

The instance to add the callback to

propstr

Name of callback property in instance

callbackfunc

The callback function to add

echo_oldbool, optional

If True, the callback function will be invoked with both the old and new values of the property, as func(old, new). If False (the default), will be invoked as func(new)

priorityint, optional

This can optionally be used to force a certain order of execution of callbacks (larger values indicate a higher priority).

Examples

class Foo:
    bar = CallbackProperty(0)

def callback(value):
    pass

f = Foo()
add_callback(f, 'bar', callback)