BCTrackingClass

Objective-C class setting up method swizzling for tracking message sending

Motivation

Designing a framework allowing an Application to instrospect its own behaviour, via the logging of its message sending. One could imagine writing a Framework that would dynamically present to the user some underused feature he could benefit from.

Installation

Drag the two files BCTrackingClass.h and BCTrackingClass.m to your project.

Usage

• Init a tracker and make it your application default one, adding these lines to your main.m :

//  main.m

#import <Cocoa/Cocoa.h>

int main(int argc, char *argv[])
{
        BCTrackingClass* tracker = [[BCTrackingClass alloc]init];
        [tracker registerTrackerAsDefault];

	return NSApplicationMain(argc, (const char **)argv);
}

• Add the relevant line for every class and methods you would like to track :

//  main.m

#import <Cocoa/Cocoa.h>

int main(int argc, char *argv[])
{
        BCTrackingClass* tracker = [[BCTrackingClass alloc]init];
        [tracker registerTrackerAsDefault];

        [BCTrackingClass setUpTrackingForClass:[BCTrackedClass class] andMethodArray:
         [ NSArray arrayWithObjects:@"doA",@"doB",@"doD:", nil]
         ];
        [BCTrackingClass setUpTrackingForClass:[BCTrackedClass2 class] andMethodArray:
         [ NSArray arrayWithObjects:@"doA",@"doB", nil]
         ];


	return NSApplicationMain(argc, (const char **)argv);
}

• Optionnal : By default, the calls are logged to NSMutableDictionnary* trackerDict . Feel free to personnalize the -(void)logCallForMethod:(NSString*)aSelectorString method if you need more.

Limitations

• Tracked methods need to be returning a -(void)
• Tracked methods can take up to three arguments, which have to be of type (id), i.e. be objective-C objects (no BOOL,int or C-struct and so on).

Failure to do so will result in at least BAD bahavior, at most memory corruption and/or loss or arguments.

Discussion

Where to set up the tracking ?

Depending on how soon your methods are suceptible to be called, you should set up the tracker in "deeper" methods. If you are not particularly insterested in early calling (i.e. before - (void)applicationDidFinishLaunching:(NSNotification *)aNotification), it looks like a good place to do so :

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
        BCTrackingClass* tracker = [[BCTrackingClass alloc]init];
        [tracker registerTrackerAsDefault];

        [BCTrackingClass setUpTrackingForClass:[BCTrackedClass class] andMethodArray:
         [ NSArray arrayWithObjects:@"doA",@"doB",@"doD:", nil]
         ];
        [BCTrackingClass setUpTrackingForClass:[BCTrackedClass2 class] andMethodArray:
         [ NSArray arrayWithObjects:@"doA",@"doB", nil]
         ];
}