Cookbook : Pipelines and Graphlines

Fairly early on you'll want a quick an easy way to link your components together. To actually build a useful system you need to set up linkages to get data from one component's outbox to another component's inbox. Pipelines and Graphlines are the two simplest and most common ways of doing this.

Pipeline and Graphline are, themselves, components. Pipeline wires components together in a long chain. For example:

from Kamaelia.Chassis.Pipeline import Pipeline

from Kamaelia.Internet.Multicast_transceiver import Multicast_transceiver
from Kamaelia.Protocol.SimpleReliableMulticast import SRM_Sender
from Kamaelia.Protocol.Packetise import MaxSizePacketiser

Pipeline( RateControlledFileReader("myaudio.mp3",readmode="bytes",rate=128000/8),
          SRM_Sender(),
          MaxSizePacketiser(),
          Multicast_transceiver("0.0.0.0", 0, "224.168.2.9", 1600),
        ).run()

Whereas a Graphline wires components together in any way you want - you specify each individual link. For example:

from Kamaelia.UI.Pygame.Button import Button
from Kamaelia.UI.Pygame.Image import Image

from Kamaelia.Util.Chooser import Chooser

from Kamaelia.Chassis.Graphline import Graphline

files = [ "slide1.gif", "slide2.gif", .... "slide99.gif" ]

Graphline(
     CHOOSER  = Chooser(files),
     IMAGE    = Image(size=(800,600), position=(8,48)),
     NEXT     = Button(caption="Next",     msg="NEXT", position=(72,8)  ),
     PREVIOUS = Button(caption="Previous", msg="PREV" ,position=(8,8)   ),
     FIRST    = Button(caption="First",    msg="FIRST",position=(256,8) ),
     LAST     = Button(caption="Last",     msg="LAST" ,position=(320,8) ),
     linkages = {
        ("NEXT",     "outbox") : ("CHOOSER", "inbox"),
        ("PREVIOUS", "outbox") : ("CHOOSER", "inbox"),
        ("FIRST",    "outbox") : ("CHOOSER", "inbox"),
        ("LAST",     "outbox") : ("CHOOSER", "inbox"),

        ("CHOOSER",  "outbox") : ("IMAGE",   "inbox"),
     }
).run()

-- 17 Dec 2006 - Matt Hammond