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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.
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