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"Redo: Package,
Classes and Methods"

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Quentin Ducasse.

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-Hello, everyone.

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In this first redo,

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we are going to look
at how to create a package,

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how to create a class within the package,

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and how to define some methods

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and see if everything
is working correctly.

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First, you can open the Pharo menu.

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Then you go to the Tools,

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and System Browser.

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There, you can see all the packages

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that are loaded
within your image,

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so there are quite a lot.

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Since we want to create a new one,
we can right-click on any of them

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and just go to New package,

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say "MyCounter", press "OK".

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Our package has been created there

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but since we do not really want
to see all the other ones,

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we can just filter them out
to "MyCounter".

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There, our package is there,
it is quite empty

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and we have a template
to create a class

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so it will be a subclass
of the class "Object"

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and we can name it there.

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Let's name it "Counter"

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and we can attribute
an instance variable to it

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so let's go with "count".

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Then, we can see
that there is this orange triangle

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in the top right corner.

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This means that your method
has not been compiled

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and in order to do so,
you can right-click and go to "Accept"

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or press the shortcut Cmd+S.

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Let's just accept.

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There it is,
our class has been created

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but there is a red exclamation mark
on the right side.

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This means that there is no comment.

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As you can see there,
there is a comment,

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but it is simply recommendations
on how to comment your class.

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You are encouraged to do it
but we are not going to do it right now.

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We are just going to do
the right method,

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so let's just go this tab right here.

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Let's double-click

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and write some accessors
to our instance variable.

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So, let's go to "count".

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This will be the getter.

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Let's just write
the "count" instance variable.

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The orange triangle is there,
so press Cmd+S.

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Our method is there.

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Now, if we want to make the setter,

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let's just count and pass it an integer.

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And the "count" variable should now

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get the value of this integer

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so we can just write this like that.

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Compile it again, Cmd+S.

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We have our two accessors.

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They have been put

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into the "accessing" protocol
automatically

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and this is correct.

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Now, let's see if we can make
all those work.

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Let's go to another tool
called the Playground.

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Let's just go to the Pharo menu,
to Tools,

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then Playground.

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And from there, we can create
a temporary variable that we call c.

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We can make it a counter

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so "c = Counter new".

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And now, we want
the count instance variable to be 7.

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And in order to see if this chain
has common effects,

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we can just call the getter "c count".

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In order to see everything,

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we can double-click at the end
so it selects everything

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and then press Cmd+P
or just right-click and go to "Print it".

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We can see that this is 7,

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this is the value we attributed to
the instance variable so it is correct.

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In this video,

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we saw how to create a package,
a class,

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some accessor methods

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and how we can visualize it
in the Playground,

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but this behavior right here,

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we might want to put this into test

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and we will see that
in the next part of the redo.