Objective-C Programming/Getting Started

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[edit] Objective C files

In objective C, files normally use the extension .m.

These objective C files are text files that contain instructions on how to write a program. For example, this is a minimal hello world program:

#import <stdio.h>
 
int main (void)
{
	printf ("Hello world!\n");
}

A C programmer may immediately see a slight difference in the preprocessor directive. This will be described in more detail in the syntax of Objective C.

[edit] Gcc

GCC, a collection of various GNU compilers, has an Objective-C package. If it is installed properly, you should be able to link against the objective-C runtime library; otherwise, you will have to consult your package system to reinstall the compiler library.

To build programs under GCC, you need to use the following command:

gcc hello.m -lobjc

Any additional files or libraries required for the program will need to be added to the command line. In addition, gcc allows compiling Objective-C files into intermediate files, which can then be linked into an output binary:

gcc -c hello.m -o hello.o
gcc hello.o -o hello

To use the object-oriented features of objective-C, you need to place the following code at the top of the file:

#import <objc/Object.h>

[edit] Other compilers

In general, the compiler name used is objc unless specified otherwise by your compiler.

In a general case, you need to have the following at the top to support objects:

#import <Object.h>