The best way to create a global class is to create a Singleton Instance.  The Apple description of this is here.

However Matt Gallagher has a great page on it here and this example is based on downloading his marco header file to simplify implementation.

Create a class called AppMain as normal.

Copy Matt’s SynthesizeSingleton.h file into your project.
If it is not done, modify the line:
– (void)release \
to be:
– (oneway void)release \
to stop the newer versions of xcode warning “Warning: Conflicting distributed object modifiers on return type in implementation of ‘release”

In the AppMain.h file

@interface AppMain : NSObject
	//Global variables and objects
	NSMutableArray *MyArrayName;
	int MyIntName;

@property (nonatomic, retain) NSMutableArray *MyArrayName;
@property int MyIntName;

+ (AppMain *)sharedAppMain;	    //- ADD THIS
In the AppMain.m file

#import "AppMain.h"
#import "SynthesizeSingleton.h"	    //- ADD THIS

@implementation AppMain

@synthesize MyArrayName, MyIntName;


Add Class To Prefix.pch

Add to MyAppName_Prefix.pch

	#import "AppMain.h"

Accessing Variables And Objects

    [AppMain sharedAppMain].MyIntName = 1234;