How to call a function when an integer changes WITHOUT using an NSTimer

[tekky]

I was wondering if there was a way to call a function when an integer goes below 1 or changes at all.

Normally I would do this:

blah.h
int playerHP;
NSTimer *timer;



blah.m
-(void)update
{
    if (playerHP < 1) {
        [timer invalidate];
        [self deathanimation];
    }
}

- (void)viewDidLoad
{
    timer = [NSTimer scheduledTimerWithTimeInterval:.01 target:self selector:@selector(update) userInfo:nil repeats:YES];

}

Is there a way to call the "update" function WITHOUT using an NSTimer? I just don't want to make like 100 timers to be watching certain integers...

ORRR... is there even a way to just check constantly if the integer changes at all and then call a function? Like for example... if a character gets gold in a game... then it sees that the gold integer changes and it automatically calls a function to save it!

I would really appreciate if anyone could help.

Thank you in advance.

[baja_yu]

Create a property for that integer with a custom setter method, in that setter you can check the value and do whatever you want to "on value change". Then in your class, when using the integer use the property/setter instead of setting its value directly.

[tekky]

Originally Posted by baja_yu

Create a property for that integer with a custom setter method, in that setter you can check the value and do whatever you want to "on value change". Then in your class, when using the integer use the property/setter instead of setting its value directly.

Have an example or any sites on how to make a custom setter method? Not sure I've done that before.

[dapis]

Originally Posted by tekky

I was wondering if there was a way to call a function when an integer goes below 1 or changes at all.

Normally I would do this:

blah.h
int playerHP;
NSTimer *timer;



blah.m
-(void)update
{
    if (playerHP < 1) {
        [timer invalidate];
        [self deathanimation];
    }
}

- (void)viewDidLoad
{
    timer = [NSTimer scheduledTimerWithTimeInterval:.01 target:self selector:@selector(update) userInfo:nil repeats:YES];

}

Is there a way to call the "update" function WITHOUT using an NSTimer? I just don't want to make like 100 timers to be watching certain integers...

ORRR... is there even a way to just check constantly if the integer changes at all and then call a function? Like for example... if a character gets gold in a game... then it sees that the gold integer changes and it automatically calls a function to save it!

I would really appreciate if anyone could help.

Thank you in advance.

Why not just use a single timer and in its selector method check for changes to all the variables in question? I'm not sure why you'd want different timers for different variables.

[tekky]

Originally Posted by baja_yu

Create a property for that integer with a custom setter method, in that setter you can check the value and do whatever you want to "on value change". Then in your class, when using the integer use the property/setter instead of setting its value directly.

What is this "on value change" command?

[X-RaY]

I guess KVO would be sufficient

small example:

@interface myModel : NSObject {
NSInteger funnyInt;
}
-(void)addObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath options:(NSKeyValueObservingOptions)options context:(void *)context;
-(void)removeObserver:(NSObject *)observer forKeyPath:(NSString *);

Implementation:

-(void)addObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath options:(NSKeyValueObservingOptions)options context:(void *)context{
	[super addObserver:observer forKeyPath:keyPath options:options context:context];
}
-(void)removeObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath{
	[super removeObserver:observer forKeyPath:keyPath];
}

@interface myObserver : NSObject {
}
-(id)initWithMyModel:(myModel*)mm
-(void)myMethod:(NSInteger)x;
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context;

implementation:

-(id)initWithMyModel:(myModel*)mm{
if(self=[super init]){
[mm addObserver:self forKeyPath:@"funnyInt" options:NSKeyValueObservingOptionNew context:nil];
}
return self;
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
	if(object.funnyInt<=1){
		[self myMethod:object.funnyInt];
	}
}

-(void)myMethod:(NSInteger)x{
NSLog("funnyint changed: %d", x);
}

by adding 'myObserver' as observer of the attribute 'funnyInt' of the class 'myModel' via the method:

addObserver:self forKeyPath:@"funnyInt" options:NSKeyValueObservingOptionNew context:nil;

automatically calls the method

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context

when funnyInt changes via the method:
[mm setValue:10 forKey:"funnyInt"];

experiment a bit with it, and you'll get the hang of it