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-Hi. In this video, we are going to look

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at how the Debugger might help you
to understand your methods better.

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I chose to use the package MyCounter

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that we implemented
in the redo of weeks 1 and 2.

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Basically, we are going to look at this
test right here, "testCounterDecrement",

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that was using and initiating a Counter
starting at 5 and decremented two times,

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and checking that the instance variable
count was actually 3.

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We can open the Debugger
on this instance

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by right-clicking
and going over to Debug tests

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or pressing the shortcut Cmd+D.

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By clicking on that, you can see
that you have got your Debugger open

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with "Break" written on top of it.

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This is because
it has created a breakpoint

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right at the beginning
of your test method.

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Within the Debugger, you can see
that there are three different areas

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that are really important. You have got,
first, the execution Stack on top.

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This execution Stack is composed of all
the different methods that were called

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in order to give the test
the ability to execute itself.

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You have got a lot of graphical
or process creation methods.

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But the one that is the most interesting
to us is the last one.

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The actual call
to testCounterDecrement.

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This area here is the body of the source
of the method that is being executed.

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The highlighted portion is a version

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that is currently
being inspected by the Debugger.

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We can get into that more later on.

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The final part consists
of all the different variables

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that the system has for now and their
value at this time in the execution.

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Finally, we can navigate in the
execution Stack and in the Debugger

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with the different functions
on top of it.

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Basically, Proceed will resume
the execution up to either its end

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or the next error. Restart will relaunch
the debug operation.

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Then, Into and Over are the ones
we will use right now.

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Into helps you dive into the source code
of the highlighted method

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while Over will make the execution
go to the next method.

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If I press Over,
we can see that right now

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startingAt is the method
being highlighted.

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This is the method we implemented
in the class side of the counter.

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If you would like to have a look at it,
we can simply press Into.

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This will bring us to another step
in the execution Stack.

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We are now in the startingAt
in the Counter class side.

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You can see that "new"
is now highlighted.

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We do not really want to dive
in the "new" source code,

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so what we will do is press Over.
This will highlight the affectation.

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And you can see here that,
for now, c has the value nil.

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When we will press Over,

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you can see that it has now
the value of "a Counter".

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We can look into it and see that for now
its attributed count is equal to nil.

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But we will set it
right away right here.

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Let us dive into this count
to see if it is actually a setter.

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We can see that it is a setter.
A nice thing we can do,

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we can highlight, for example,
anInteger, press Cmd+D to print it.

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You can see that it is equal to 5.

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You can see that this part there
is equal to nil

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while this part here is equal to 5.

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This is extremely useful.
We press Over.

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This will execute the method count

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and we can now look
at our temporary variable, c,

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and look on the Raw tab that it now has
a value 5 as its count attribute.

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This will return the c, OK?

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Right now, we came back
to our testCounterDecrement body,

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and we can see that c
is still equal to nil.

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But we are highlighting the affectation,
so by pressing Over,

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we will give c a value,
the value of "a Counter" starting at 5.

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Now, it is equal to "a Counter"
and if we go to the Raw tab,

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you can see that count is equal to 5.

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This is really helpful to understand
the objects you work with.

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Right now,
the decrement method is highlighted.

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Once again, we dive into and look at,
for example, count.

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Now, it is equal to 5
and "count -1" is equal to 4.

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So, basically it will simply
do this affectation.

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Press Over, Over, Over.

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If we look back at our counter,

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we can now see that its count
is equal to 4. Press Over again,

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Over again,
and now we can look back at our c.

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It should have a count equal to 3
because we decremented two times.

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We can inspect this
and we know that it is equal to 3,

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so everything should be fine,
we can press Proceed.

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This is a small look into the Debugger,

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but it is really helpful for you
to understand

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both the workflow of your methods
and your objects better.

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Another thing that is important to note

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is that you can do the same thing
from within the Playground.

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For example, if I copy/paste
this piece of code,

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highlight it, right-click,
and go over to Debug it,

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or you can press
the Cmd+Shift+D shortcut,

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it will open the Debugger where you can
do basically the same thing.

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If I press Over a couple of times,
we can look inside the value of c,

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see that it is a counter
with a value of 5 as count.

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We can decrement it,
look back at it, it is equal to 4.

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You can do a couple of things and
the last thing that you should not forget

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is that the Debugger is a working
environment, and if, for example,

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I dive into the method decrement,
and I change it to -2,

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and I save this,
because you can save this.

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The orange corner
meaning that it is not saved.

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So, I save it pressing Cmd+S,

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and my decrement method is now this:
"count := count -2".

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If I press Proceed...
I can just close it.

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If I go over to my test,
it might not work

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because we changed our decrement method,
and if I click on it,

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you can see that I obtain 1
instead of 3.

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So, the Debugger
is a working environment,

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and it will really help you understand
the flow of your methods

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and your objects better.
So I can only encourage you to use it.