Objective-C Fundamentals

Variable naming conventions
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As IDEs have become more powerful with features such as Code Sense (Apple’s equivalent
to IntelliSense), the use of Hungarian notation has quickly lost favor among developers.
It’s now quick enough to determine the data type associated with a variable
without encoding it into the name. Most usage of Hungarian notation is now confined
to C-based source code; it’s uncommon to see this convention used in applications that
embrace Objective-C. This is not to say that other naming conventions have also faded;
for example, camel case is still popular among Objective-C developers.
B.1.2
B.1.3
Camel case
It’s helpful to make identifiers as descriptive and self-documenting as possible. As an
example, a variable named CountOfPeople is more meaningful than a variable simply
named n.
Because identifiers can’t contain spaces, one common technique for achieving this
goal is to capitalize the first letter of each word, as seen in the variable name CountOf-
People. This technique is named camel case for the “humps” the uppercase letters
spread throughout the identifier. Another alternative to camel case is the use of
underscores to separate words: Count_Of_People.
Namespaces
When your applications start getting more complex or you start to use code developed
by a third party, one problem you may come across is a clash between identifiers. This
occurs when two separate parts of the application attempt to use the same identifier to
represent different things. For example, your application may name a variable Counter,
and a third-party library might name a class Counter. If you were to refer to Counter
in your source code, the compiler would be unable to determine which item you were
referring to.
Some programming languages resolve this problem via a mechanism called
namespaces. A namespace allows you to group related identifiers into separate groupings
or containers. For example, all the code written by Apple could be placed inside
one namespace, and all the code written by you could be placed inside another. Each
time you reference a variable or function, you must provide not only the name of the
identifier but also its containing namespace (although this may be implied rather
than explicit). In this manner, if two regions of code attempt to reference something
called Counter, the compiler can differentiate between the two interpretations and
understand your intent.
The C programming language doesn’t provide a concept equivalent to that of
namespaces, but it’s possible to simulate enough of their behavior to avoid collisions
by using commonly agreed-upon prefixes for your identifiers.
A good example of this technique is the venerable NSLog function. This function
can be thought of as having the name log in a namespace called NS. NS is the
namespace prefix Apple uses for the Foundation Kit library; as such, it would be unwise
to start the name of any of your variables or functions with the NS prefix because it
would increase the likelihood of its clashing with a preexisting Apple function.