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-We are in part 5 of the redo

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and we are looking at how to initialize
our objects correctly.

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What we did in the previous parts

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was calling "new"
to the class we want to instantiate

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and then attributing manually the values
we want to the instance variables.

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Let's see what happens

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if we simply call "c increment"
right now.

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Let's just do it, Cmd+P.

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Okay, so "+ was sent to nil".

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This means that "count" by default,

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which we have not initialized
in any way,

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will have as value "nil",
which Pharo chose for us.

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This is not
the most useful default value

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and imagine we could put "0".

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Let's write a test
that would cover this case.

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We will not need...

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Let's rename it first, "testInitialize".

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We will not need these two lines.

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We want right after creation

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that the "count" instance variable
is equal to 0.

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Let's save this. Okay.

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Now, if we initialize it,

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let's run the test.

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It fails because we have not
changed anything

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and the default value is still "nil".

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In order to change it,
we have to define an "Initialize" method.

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This method is called
at the creation of any object

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so it is good practice to call
the superclass initialization methods

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and then implement the behavior
we wanted to have,

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so "count" is equal to 0.

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Okay, save this.

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The test method has been detected.
Let's run it.

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It is working so this is great.

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We have the default behavior of putting
the instance variable count to 0.

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Now, imagine we want
to have a value of 5 at creation.

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We could change the "initialize" method

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but we would like to keep this one
as default.

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We can write a class method
that would handle this for us.

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Let's write a test.

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Let's write the "testStartingAt5".

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Instead of "new",
we will call it "startingAt: 5".

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We want to assert
that the count would equal 5.

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Okay, let's save this.

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The method is not detected,
but it is normal. Let's run it.

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Okay, "Instance of Counter class
did not understand #startingAt".

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We have to implement the class method
"startingAt" in the Counter.

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In order to implement a class method,
you go to the class you want.

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"Inst. side",
that is where we are right now.

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Let's go to "Class side"

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and implement "startingAt: anInteger".

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Okay and we want to write:
"self new count: anInteger".

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This means a new counter will be created

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and the instance variable will be
the integer we will provide.

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Let's save this
and now if we run our tests,

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they are all green. Cool.

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Let's write a final test
that handles most of our functions.

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We will call it "StartingAt5Increment".

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We will start at 5,

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but we will just add
an increment step right there

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and then call "count"
on the incremented counter.

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This should be 5 incremented, so 6.

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Let's see.

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If we run all our tests,

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the six ran and the six passed.

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This is a great time
to commit your changes.

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We will go to the Iceberg Working copy,

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press Commit

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and write...

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"Initialization methods (tested)".

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Let's commit that.

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We learned
how to initialize correctly your objects

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with a default behavior

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and provide class methods
to have more examples

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of working instances
for classes you want.