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

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and how we can use them in Pharo
at different levels.

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Refactorings were introduced
in Smalltalk in 1995.

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They are extremely handy because they
allow you to refactor pieces of code,

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change the relation between your classes
and methods, etc., extremely quickly.

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I have taken back the counter
we made in the redo of week 2.

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It still has the four methods
we implemented:

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count, count:, decrement, increment,
and then the tests.

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You can check that they are still green.
Cool.

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The first level of refactoring
you can have is within the class.

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You can right-click on the class,
go to...

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You will have Rename, Copy,
Jump to test class, Remove, etc.

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Then, you have got Refactorings

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that will allow you
to insert subclass, superclass,

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and/or change this class
from a package to another.

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We will look at Rename.
Let's click on it.

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We will just rename it "Counter2".

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Ok.

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You can see that our counter
is now renamed "Counter2".

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If you go to the CounterTest,

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we can see
that every occurrence of "Counter"

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has been replaced by "Counter2".

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You can run the tests,
check that they are still green.

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It is the case. Great.

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Now, we will look into another level
of refactoring that is methods.

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If you right-click on a method,
for example "increment",

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you still have Rename
because it is extremely useful.

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So it has been moved to another level.
But you can go to the Refactorings tab

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and you can see that you have Push up,

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so you can bring this method
to its superclass or subclass.

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Then you have Move to class side
or Move to another class,

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Move to another package.
You can Add argument, etc.

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We are going to look
into the Rename for now.

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We press Rename,

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and we would like to rename
our "increment" method to "increment2".

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Press Rename.

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You can see that this will modify
all 9 implementors.

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But we only have one.

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This might mean that we are modifying
things that we would not like to.

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So, let's press No.

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Just to remind you, the shortcut
for implementors is Cmd+M.

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So, let's press that.

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You can see that there are many
implementors of increment.

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Some of them will rather not change,
such as JobProgressBarMorph.

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In order to contain our actions
to the actual package,

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we will set up a scoped view.

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You can either right-click
and select Set up scope

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or you can simply,
since we only have one package,

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press the button Scoped View.

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We will do that for now. Scoped View.
Now, if we right-click

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and try to rename it again,
"increment2", Rename,

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this time we have
only modified this method,

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and you can see that this would be
the changes that would apply.

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It will add a method called "increment2"
in the class Counter2. That is great.

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That will change the test path
using increment,

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changing "increment" to "increment2",

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and then remove
the actual increment method.

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That is perfect,
that is exactly what we want.

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Let's just press Apply.

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You can see that we now have
a method increment2.

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If we go to the testCounterIncrement,
you can see that it changed.

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Now, we are going to look at another
level of refactoring which is protocols.

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You can right-click on them,
you can rename them,

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you can remove empty protocols.

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Basically, this happens
when you create new methods,

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tag them into protocols, and then remove
them without changing the protocol.

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This might happen.
You can simply press this button

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or you can categorize all methods
that are uncategorized.

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The last level of refactoring that you
can use is from within the source code.

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Let's go, for example,
to testCounterStartingAt5.

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We will just select that, highlight it,
and you can right-click

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and go to Source code, and there you
will have all the possible refactorings,

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Rename, etc.,
and you can extract methods.

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This is interesting because...
Let's click on it.

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We can say we will call it
"startingAt5".

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Rename.

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You can see
that we now have a method there

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that is doing exactly
what we have highlighted earlier on.

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You can see that it is doing
"Counter2 startingAt: 5",

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and then, in the test, you can see
that it is calling "self startingAt5".

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So, it has really extracted
what we highlighted in the method.

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This might not be the best idea here

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because we are talking
about a test class.

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But it is just to give you the idea that
you can simply highlight a piece of code

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to extract its method.

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I really encourage you to learn
refactorings and how you can use them

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because you will
really be faster in your writing.

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You will simply develop faster
and maybe better

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because this will help you to not forget
some references you might have written

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to a method when you rename it
or it will save you time

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when you remove a method
then write it back again.

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You can simply refactor, push up,
push down, move to class side.

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Please, use refactorings,
they will really help you.