This workshop will be retired on May 1, 2025.
Heads up! To view this whole video, sign in with your Courses account or enroll in your free 7-day trial. Sign In Enroll
Preview
Start a free Courses trial
to watch this video
In this video, we’ll set breakpoints that suspend the execution of the code and allow us to inspect and modify the state of our application.
Related Discussions
Have questions about this video? Start a discussion with the community and Treehouse staff.
Sign upRelated Discussions
Have questions about this video? Start a discussion with the community and Treehouse staff.
Sign up
While debugging using logs and trace
points works well for simple scenarios,
0:00
in more complex scenarios you'll probably
find this technique to be cumbersome.
0:05
This is where breakpoints save the day.
0:09
So what exactly is a breakpoint?
0:11
A breakpoint is a way to indicate
that code execution should be
0:13
paused at a specified place.
0:17
When a break point is set, and
the code is run with the debugger.
0:19
Execution of the code is suspended
right before the line of code
0:23
associated with
the breakpoint is executed.
0:26
We can set many breakpoints
throughout the code base.
0:29
Later, we'll discover
how we can easily manage
0:31
all the break points
set in our application.
0:34
In this video, we'll set breakpoints that
will suspend the execution of the code and
0:36
allow us to inspect and
modify the state of the application.
0:41
Let's set a breakpoint right here
before we go into this while loop.
0:45
Now, let's run the debugger.
0:49
As you can see, the program has paused
before printing out the menu options.
0:53
Now, we can step through the code
line by line if we want to.
0:58
Because we're in the debugger, we now have
a bunch more buttons here on the toolbar.
1:02
We have Show Next Statement,
Step Into, Step Over, and Step Out.
1:07
We also have Restart and Stop here.
1:14
Step into, let's say step into any
methods that are on the current line.
1:17
In this case, we have the prompt method.
1:22
So if we click Step Into, we'll go into
the prompt method cooking step into
1:25
when there isn't a method to step into or
just step us over the next line of code.
1:30
If we don't want to step into a method,
we can click the Step Over button.
1:36
Let's say we don't want to
go into the display method,
1:42
I'll click the step over button.
1:45
The display method still runs like normal,
1:47
but the debugger didn't
pause inside of it.
1:50
And I'll click step over
when I get to CLI.Prompt.
1:53
As you can see the CLI.prompt
method was called and
1:57
I'm prompted to select an option.
2:01
I'll select one here.
2:04
Now, we're at the next line.
2:06
We can run the rest of this prompt
method without pausing by clicking
2:08
the step out button.
2:12
This step says out of
the current method and
2:13
now we're back where
menu.prompt was called.
2:16
We might be looking around the code
while the debugger is paused.
2:20
So if we ever lose track of where the
debugger is paused we can click the show
2:24
next state button and we're brought back
to where the yellow arrow is right here.
2:28
Also, we can click the Continue button
to run until another breakpoint.
2:34
We can also have the program restart or
stop it completely.
2:46
Breakpoints don't have to
be set on entire lines.
2:52
A good example of this is when setting
a breakpoint on an auto property
2:56
where the getter and
setter are on the same line.
3:00
By default if we click to create
a breakpoint on the Name property
3:03
only the getter is highlighted here.
3:07
This means this breakpoint will
only be hit when getting the value
3:09
of the name property.
3:13
If we were to run this right now,
3:14
this breakpoint would not be hit when
setting the value of the name property.
3:16
However, sometimes we want to
pause before a property is set,
3:21
we can do that by first highlighting
the set statement, right clicking,
3:24
going down to Breakpoint and
clicking Insert Breakpoint.
3:30
We now have two breakpoints on this line,
one on the getter and one on the setter.
3:34
This trick is also helpful when
setting breakpoints on lines that may
3:39
have multiple expressions in them such as
3:42
ternary IF statements that
are written on a single line.
3:45
You need to sign up for Treehouse in order to download course files.
Sign upYou need to sign up for Treehouse in order to set up Workspace
Sign up