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In this video, I’d like
to show you more

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advanced analysis you can do
on code with Nautilus.

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So let’s open Nautilus.
We consider for instance

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a simple class, NumberParser.

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Now we look at what

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we call Senders and 
Implementors.

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Often, we know someone
is fluent in Pharo when

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he has understood how to
use Senders and Implementors

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to find information.
So let’s have a look:

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I consider a method,
I’d like to know what

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calls this method: 
what do I do?

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I use Senders Of.

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What will I get with Senders Of?

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I get here only one method

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which calls Senders Of,
it is called 

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ReadExponent and it calls
ExponentLetters.

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It is an interesting information.

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Now let’s imagine I go
in the public

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protocol, I choose
NextInteger. I ask the Senders.

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I will get this potential

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Senders list.

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In fact, these are all the places
that send the NextInteger message.

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Here I see I am in the
NumberParser

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class, and I call
Self.

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As I use Self to do a call, it

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will necessarily
be the method I have here

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Now on the packages or the XML
class, it is not so

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obvious because I don't necessarily 
know, as Pharo

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is a language with no types,
I don't know for sure

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if this is the method concerned.

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In fact, the system shows
that a message

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with the same name has been sent.

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In order to check this, 
I can for instance

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say that I'd like to know

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what are the implementors,
how many times is

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the method implemented in the
system.

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To do this, I will select
Implementors Of.

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Implementors Of. Ah bah
look, whereas in the other

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case I only had one method, so it 
was necessarily the one

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that was called, here I have
several ones.

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This method, NextInteger, is 
defined

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on NumberParser, but it is
also defined on XMLInteger.

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XMLInteger is even defined on
two different

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classes. So I see that these

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methods, these calls are 
message sends

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calls and they will be resolved
and the methods selected.

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You see that Sender and 
Implementor are

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very important.
With Implementor you will

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see all the system's classes 
implementing a method.

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With Sender you will see
all the calls made to a method.

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Senders are really very important
because

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they enable you to look at
examples,

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to find how a method is invoked.

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Here I've selected a method 
with no argument,

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but if I had chosen a method with
an argument,

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for instance Number, 
NextNumberBase and I click

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on Sender: what will it

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show me? I have an argument,
and I see it is

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the base.

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Here it appears it is not 
an argument,

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it is just a call that has an
argument.

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But in this test here, 
I see that

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if I instantiate
NumberParser on Stream,

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and then I send it the message
NextNumberBase

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and the argument 10.

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It makes me understand how

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I have to use the API.

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It is so much used that there
are keyboard shortcuts.

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Nautilus was first designed
so that you can

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do all these operations
without touching the mouse.

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Here notice that B means
browse.

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So we will do Browse Sender,
N is for Sender's N.

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Browse Implementor, M
is for Implementor.

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If I select only "NextNumber" 
for instance,

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and I do Browse N, I will
get

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NextNumber's Senders.

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In the same way, if I select 
I get them.

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Now if I want to get the
Implementors, Browse M,

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I get the Implementors.

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In the same way about classes,
I'd like 

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to know what are the other system
classes using

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NumberParser.
To know this, 

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I select Analyze,
I have Class

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references. And I get all

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the classes. I get all the methods
using...

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Here I see they are mainly tests.

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Look: in  ClassInteger, I call

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the Parser.

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Here, the tip to understand
is to remember the

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keyboard shortcut,

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Browse shift N, with a 

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capital letter because it is
the same as to 

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invoke a method, except here
we want

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to invoke a class and a class
is bigger than

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a method, so we have a capital
letter.