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June 27, 2012 00:17
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Global Variables in Objective-C (Singleton)
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| URL: http://sree.cc/iphone/global-functions-and-variables-in-objective-c | |
| How to make Global Variables (Singleton) in Objective-C | |
| Step 1: Open your XCode project and add a new class. | |
| In your XCode > ‘Group & Files’ colum > Right click on the classes folder > Click ‘Add > New File..’ > Select ‘Objective-C class’ (ensure its a sub class of NSObject) > Click ‘Next’ > Enter the new class name (in this example, GlobalData) > Finish | |
| Step 2: The .h file | |
| @interface GlobalData : NSObject { | |
| NSString *message; // global variable | |
| } | |
| @property (nonatomic, retain) NSString *message; | |
| + (GlobalData*)sharedGlobalData; | |
| // global function | |
| - (void) myFunc; | |
| @end | |
| Step 3: The .m file | |
| #import "GlobalData.h" | |
| @implementation GlobalData | |
| @synthesize message; | |
| static GlobalData *sharedGlobalData = nil; | |
| + (GlobalData*)sharedGlobalData { | |
| if (sharedGlobalData == nil) { | |
| sharedGlobalData = [[super allocWithZone:NULL] init]; | |
| // initialize your variables here | |
| sharedGlobalData.message = @"Default Global Message"; | |
| } | |
| return sharedGlobalData; | |
| } | |
| + (id)allocWithZone:(NSZone *)zone { | |
| @synchronized(self) | |
| { | |
| if (sharedGlobalData == nil) | |
| { | |
| sharedGlobalData = [super allocWithZone:zone]; | |
| return sharedGlobalData; | |
| } | |
| } | |
| return nil; | |
| } | |
| - (id)copyWithZone:(NSZone *)zone { | |
| return self; | |
| } | |
| - (id)retain { | |
| return self; | |
| } | |
| - (NSUInteger)retainCount { | |
| return NSUIntegerMax; //denotes an object that cannot be released | |
| } | |
| - (void)release { | |
| //do nothing | |
| } | |
| - (id)autorelease { | |
| return self; | |
| } | |
| // this is my global function | |
| - (void)myFunc { | |
| self.message = @"Some Random Text"; | |
| } | |
| @end | |
| Access Global: | |
| #import "GlobalData.h" | |
| Access Global Variable: | |
| [GlobalData sharedGlobalData].message | |
| Access Global Function: | |
| [[GlobalData sharedGlobalData] myFunc]; |
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This help me so much! Thank you!