Objective-C Basic Syntax
You have seen a basic structure of Objective-C program, so it will be easy to understand other basic building blocks of the Objective-C programming language.
Tokens in Objective-C
A Objective-C program consists of various tokens and a token is either a keyword, an identifier, a constant, a string literal, or a symbol. For example, the following Objective-C statement consists of six tokens −
NSLog(@"Hello, World! \n");
The individual tokens are −
NSLog
@
(
"Hello, World! \n"
)
;
Semicolons ;
In Objective-C program, the semicolon is a statement terminator. That is, each individual statement must be ended with a semicolon. It indicates the end of one logical entity.
For example, following are two different statements −
NSLog(@"Hello, World! \n");
return 0;
Comments
Comments are like helping text in your Objective-C program and they are ignored by the compiler. They start with /* and terminate with the characters */ as shown below −
/* my first program in Objective-C */
You can not have comments with in comments and they do not occur within a string or character literals.
Identifiers
An Objective-C identifier is a name used to identify a variable, function, or any other user-defined item. An identifier starts with a letter A to Z or a to z or an underscore _ followed by zero or more letters, underscores, and digits (0 to 9).
Objective-C does not allow punctuation characters such as @, $, and % within identifiers. Objective-C is a case-sensitive programming language. Thus, Manpower and manpower are two different identifiers in Objective-C. Here are some examples of acceptable identifiers −
mohd zara abc move_name a_123
myname50 _temp j a23b9 retVal
Keywords
The following list shows few of the reserved words in Objective-C. These reserved words may not be used as constant or variable or any other identifier names.
| auto |
else |
long |
switch |
| break |
enum |
register |
typedef |
| case |
extern |
return |
union |
| char |
float |
short |
unsigned |
| const |
for |
signed |
void |
| continue |
goto |
sizeof |
volatile |
| default |
if |
static |
while |
| do |
int |
struct |
_Packed |
| double |
protocol |
interface |
implementation |
| NSObject |
NSInteger |
NSNumber |
CGFloat |
| property |
nonatomic; |
retain |
strong |
| weak |
unsafe_unretained; |
readwrite |
readonly |
Whitespace in Objective-C
A line containing only whitespace, possibly with a comment, is known as a blank line, and an Objective-C compiler totally ignores it.
Whitespace is the term used in Objective-C to describe blanks, tabs, newline characters and comments. Whitespace separates one part of a statement from another and enables the compiler to identify where one element in a statement, such as int, ends and the next element begins. Therefore, in the following statement −
int age;
There must be at least one whitespace character (usually a space) between int and age for the compiler to be able to distinguish them. On the other hand, in the following statement,
fruit = apples + oranges; // get the total fruit
No whitespace characters are necessary between fruit and =, or between = and apples, although you are free to include some if you wish for readability purpose.
