Collaboration Diagrams Video Lecture | Embedded Systems (Web) - Computer Science Engineering (CSE)

um L stands for unified modeling
language and we're currently on version
2 what I'm going to show you here is
something called the collaboration
diagram that comes from version 1 of UML
this has been replaced in version 2 by a
communication diagram however I actually
believe that a collaboration diagram is
far better to model how objects
communicate within a visual basic
program consequently I'll be
illustrating a collaboration diagram as
and other means of us trying to
understand how objects communicate with
one another when a computer program
actually executes
let's look at the component parts that
make up a collaboration diagram firstly
what we can see here is we have a
rectangular box and inside the box we
have the word class-a now this simply
represents a class so if we wish to
refer to a class in the collaboration
diagram this is how we would actually do
it we would have a rectangular box with
the word clase in it or whatever the
name of the class happened to be so the
text there simply is saying a rectangle
containing the name of a class
represents a class now the thing is
visual basic allows you to use a class
directly and I don't think that's a good
idea because it kind of goes against
object orientation however because it
does allow it I think this is a useful
component to have something that
represents a class but you will see that
I won't use this very often at all if at
all when I actually write my designs out
before I come here we've got a rectangle
again but this time we have Class A and
a colon and all of it has been
underlined now what this represents if
we were to see this in a collaboration
diagram will be an instance of class a
in other words an object but this is a
particular kind of inst this is an
object that doesn't have a name now
we've really seen this already when you
start a windows form application in
Visual Basic you get the first form by
default when you run the program and we
don't know the name of that is we
weren't responsible for giving it a name
so this is useful for those type of
occasions so if we look at the text
associated with this it says a rectangle
containing the name of a class of : as
we can see and is all on the line well
that represents an unnamed instance of
the name class that we see before us in
other words this is an object of class a
that we don't know the name of if we
have a look at this one here this again
is a rectangle and inside we have the
text Class A again there we can see the
colon and before the column we can see
it as object name and all of it on the
line now this is an instance of Class A
that has the name object name and
therefore we can look at the text for
this one
and this is a rectangle containing the
name world class the name of the object
either side of a colon and is all on the
line then that represents a named
instance of the class we can see before
so this is a named instance of class a
this here is something that allows us to
write some notes about a collaboration
dying on them we have drawn so in other
words it's just like a comment in a
program I can put them text in this area
and that's quite handy if I want to
convey something to my fellow colleagues
when we're designing a particular
program so we can see here this shape
represents a way of commenting on a
diagram and it's quite simply referred
to as a note if we look at the mall
side-by-side we can see the first one
here represents a class this one
represents an unnamed instance of the
class ie an object an unnamed object
this one here represents a named
instance of the class ie a named object
and this one is where we can put notes
about any diagrams that I wish to draw
a collaboration diagram allows a
programmer and designers to actually
work out how objects are going to talk
to each other when the program is
actually executing and the key is before
we actually start writing our code so a
collaboration diagram allows us to look
at objects as if they were in an
execution space talking to each other
passing in messages before I sit down at
a keyboard and type any code in and
that's key to understanding why we have
collaboration Doug in this particular
playlist what I'll be showing you is how
to read collaboration diagrams and I'll
be drawing reference to cold we've
already seen and once we know how to
read them then we can start designing
with them how we design won't appear in
this particular playlist but I think it
is important that we're able to refer to
collaboration diagrams and code and
relate them to one another and what I
can stress that when you write large
systems it is important to give great
consideration to how objects talk to
each other and a collaboration diagram
and to be fair the new communication
diagram allows you to do this just that
I have a preference for a collaboration
diagram and it's highly likely that the
ones we'll be using are these two here
this one which is the unnamed instance
of class a and this one which is the
named instance of class a
instead of thinking of execution spaces
I can now think about objects messaging
each other using the collaboration
diagram so I'm going to start off by
saying that I have an object coming to
existent and this object here is an
instance of Class A now I can tell that
because to the right of the colon it
says Class A and it's underlined which
tells me it's an instance ie is an
object but I don't know its name so this
is an unnamed instance of Class A now
let's say within this instance there is
some code that's capable of producing
another object and this is the other
object here now this is an instance of
Class B how do I know that because I
look at the colon and to the right of
the colon as I look at it it says Class
B the whole lot on the line and to the
left of the column we've got the name of
the actual object itself which I've
simply called
object name the instance of Class A
produce this instance of Class B
consequently we have what's called a
line of visibility between them as you
can see here of the instance of Class A
was responsible for producing the
instance of Class B and I can now send a
message between them so I would show a
message simply as this with the name of
the message and an arrow showing the
direction in which the message went so
here I'm quite clear that I'm thinking
of a program that has an object which is
an instance of Class A in this case
creates an instance of Class B and then
sends a message to the instance of Class
B so I'm beginning to look at how
objects communicate using the
collaboration diagram and I haven't
started writing any code yet
you