Methods to be implemented

def sequence(self)
def process(self, identity, context, *args, **kwargs)

The sequence method must return an integer that will dictate sequence on when it must be executed.

The process method is the entrypoint for each plugin and this is where our plugin logic must reside. This method has two important parameters namely identity and context. Currently the identity is the name of the plugin (i.e. defined in the yapsy configuration file that is particularly the Name attribute) and the context contains some information about the plugin. Also this method must return one of the predefined status.

ISequencialPlugin Return Status

Example 1. Simple Plugin Implementation

import mg_conveyor as conveyor
class PluginOne(conveyor.ISequencialPlugin):
    def sequence(self):
        return 100
    def process(self, identity, context, *args, **kwargs):
        print("Hello Worlds.")
        return conveyor.STATUS_SUCCESS

Using the context Parameter

The context parameter contains some information about the plugin like its status (i.e. CONTEXT_KEY_STATUS) and its instance (i.e. CONTEXT_KEY_PLUGIN_OBJECT). This parameter is just a simple dictionary. By default each plugin has its own context inside the context with the key as its identity (i.e. context[identity]). Thus, to get the plugin object of the current plugin we should access it like the following snippet inside the process method.

pluginObj = context[identity][CONTEXT_KEY_PLUGIN_OBJECT]

Pre-defined Context Keys per identity

The context has another purpose that it can hold custom plugin information. To add a new entry to the context it is better to add it under the identity key. This can be done by the snippet below (i.e. inside the process method):

plugin_context = context[identity]
plugin_context['item1']='This is item 1'
plugin_context['item2']='This is item 2'

More over this context is shared by all the plugins loaded by the conveyor. Therefore, we can use the context to pass information between plugins. For example the result of the first plugin can be stored in the context and that item will be processed by the following plugin.

Method to be implemented

def use(self, *args, **kwargs)

The use method must contain the implmentation on what the ISequencialPlugin implementaion demands it to do according to what it's purpose as a tool. It can return any type therefore the a proper documentation of the return type is necessary.

Built-in Properties

The IUtilityPlugin has built-in properties as we can see in the following table:

Acquiring IUtilityPlugin from context

To acquire an instance of the IUtilityPlugin we must know its identity (i.e. Name attribute in yapsy configuraiton file.). Once we have the instance we can call it's use method.

Example 2: Acquiring IUtilityPlugin

If have Utility as the identity then in the process method of the ISequencialPlugin implementation we can retrieve its instance like in the snippet below:

def process(self, identity, context, *args, **kwargs):

    utilObj = context['Utility'][conveyor.CONTEXT_KEY_PLUGIN_OBJECT].use()

plugins/helloworld_plugin.py

import mg_conveyor as conveyor
class PluginOne(conveyor.ISequencialPlugin):
    def sequence(self):
        return 100
    def process(self, identity, context, *args, **kwargs):
        print("Hello World.")
        return conveyor.STATUS_SUCCESS

plugins/helloworld.yapsy-plugin

[Core]
Name = Hello World
Module = helloworld_plugin

[Documentation]
Author = Ronaldo Webb
Version = 0.1
Website = http://www.ronella.xyz
Description = Test only

helloworld.py

import mg_conveyor as conveyor

if __name__ == '__main__':

    conv=conveyor.Conveyor()
    conv.loadPlugins(["plugins"])
    conv.start()

plugins/plugin1.py

import mg_conveyor as conveyor
class Plugin(conveyor.ISequencialPlugin):
    def sequence(self):
        return 100

    def process(self, identity, context, *args, **kwargs):
        plugin_context = context[identity]

        plugin_context['Message'] = "From plugin 1"

        return conveyor.STATUS_SUCCESS

plugins/plugin1.yapsy-plugin

[Core]
Name = Plugin1
Module = plugin1

[Documentation]
Author = Ronaldo Webb
Version = 0.1
Website = http://www.ronella.xyz
Description = Test only

plugins/plugin2.py

import mg_conveyor as conveyor
class Plugin(conveyor.ISequencialPlugin):
    def sequence(self):
        return 200

    def process(self, identity, context, *args, **kwargs):

        #Plugin1 is the Name found in plugin1.yapsy-plugin
        plugin1_context = context['Plugin1']


        print("I'm in plugin 2...")
        print("Message from plugin 1: " + plugin1_context['Message'])
        return conveyor.STATUS_SUCCESS

plugins/plugin2.yapsy-plugin

[Core]
Name = Plugin2
Module = plugin2

[Documentation]
Author = Ronaldo Webb
Version = 0.1
Website = http://www.ronella.xyz
Description = Test only

context_usage.py

import mg_conveyor as conveyor

if __name__ == '__main__':

    conv=conveyor.Conveyor()
    conv.loadPlugins(["plugins"])
    conv.start()

plugins/parameter.py

import mg_conveyor as conveyor
class PluginOne(conveyor.ISequencialPlugin):

    def sequence(self):
        return 100

    def process(self, identity, context, *args, **kwargs):
        print("Argument 1: " + args[0])
        print("Arguemnt 2: " + args[1])
        print("Parameter 1: " + kwargs['param1'])
        print("Parameter 2: " + kwargs['param2'])

        return conveyor.STATUS_SUCCESS

plugins/parameter.yapsy-plugin

[Core]
Name = Parameter Passing
Module = parameter

[Documentation]
Author = Ronaldo Webb
Version = 0.1
Website = http://www.ronella.xyz
Description = Test only

process_parameter.py

import mg_conveyor as conveyor

if __name__ == '__main__':

    conv=conveyor.Conveyor()
    conv.loadPlugins(["plugins"])
    conv.start("arg0"
        , "arg1"
        , param1="This is parameter 1"
        , param2="This is parameter 2")

utility.py

import mg_conveyor as conveyor

class Utility(conveyor.IUtilityPlugin):

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

    def use(self, *args, **kwargs):

        self.localContext['Message'] = "I'm in Utility plugin"
        return "This is a test."

utility.yapsy-plugin

[Core]
Name = Utility
Module = utility

[Documentation]
Author = Ronaldo Webb
Version = 0.1
Website = http://www.ronella.xyz
Description = Test only

sequence.py

import mg_conveyor as conveyor

class PluginOne(conveyor.ISequencialPlugin):
    def sequence(self):
        return 100

    def process(self, identity, context, *args, **kwargs):

        utilCtx = context['Utility']
        utilOutput = utilCtx[conveyor.CONTEXT_KEY_PLUGIN_OBJECT].use()

        if 'util_message' in kwargs:
            kwargs['util_message'](utilCtx['Message'])

        if 'util_output' in kwargs:
            kwargs['util_output'](utilOutput)

        return conveyor.STATUS_SUCCESS

sequence.yapsy-plugin

[Core]
Name = Sequence
Module = sequence

[Documentation]
Author = Ronaldo Webb
Version = 0.1
Website = http://www.ronella.xyz
Description = Test only

utility_usage.py

import mg_conveyor as conveyor

if __name__ == '__main__':

    conv=conveyor.Conveyor()
    conv.loadPlugins(["plugins"])
    conv.start()