Objective-C Fundamentals

Creating your own data types
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Both type definitions say that struct box can also be referred to by the name cube.
This allows you to declare variables in your application as follows:
struct box a;
cube b;
The new data type cube created via the typedef statement is purely an element of syntactic
sugar. As far as the Objective-C compiler is concerned, struct box and cube both
mean the same thing: you’ve specified alternative names for the developer’s convenience.
Although you can use typedefs to rename enums, structs, and unions, they can also
be beneficial to provide alternative names for primitive data types such as int or
double. One problem with the basic numeric data types is that they can sometimes
seem meaningless in isolation. If you were presented with the following statement
double x = 42;
you wouldn’t be able to determine what the value 42 represents. Is it a temperature,
weight, price, or count? Giving an existing data type a new name can make such a statement
more self-documenting. As an example, listing 2.2 contains a type definition that
can be found in the Core Location API, which is responsible for GPS positioning.
Listing 2.2
Example typedef from Core Location’s CLLocation.h header file
// CLLocationDegrees
// Type used to represent a latitude or longitude coordinate
// in degrees under the WGS 84 reference frame. The degree can
// be positive (North and East) or negative (South and West).
typedef double CLLocationDegrees;
Although the type definition provides an alternative name for double, it enables us to
declare a variable using a statement similar to the following:
CLLocationDegrees x = 42;
This new statement, although essentially identical to the previous, makes the meaning
of the value 42 much more apparent.
Good variable names are equally as important
Although the use of the typedef statement can provide more descriptive names to
existing data types, this feature should not be relied on in isolation. For example, look
at the given variable declaration:
CLLocationDegrees x = 42;
This could have arguably been made even more descriptive by using a better variable
name instead of the typedef. For instance:
double currentHeadingOfCar = 42;
In general, try to be as descriptive as possible with any form of identifier, be that a
variable, datatype, method, or argument name. The more self-documenting your
code, the easier it is to maintain and come back to after periods of inactivity.