How to pass arguments when calling function with timer in objective c

Question

-(void)setX:(int)x andY:(int)y andObject:(Sprite*)obj
{
    [obj setPosition:CGPointMake(x,y)];
}

Now, I want to call above method, using following

Answer 1

You'll need to used +[NSTimer scheduledTimerWithTimeInterval:invocation:repeats:] instead. By default, the selector used to fire a timer takes one parameter. If you need something other than that, you have to create an NSInvocation object, which the timer will use instead.

Answer 2

If you have a fairly complex set of arguments that you want to use to invoke the method, I would recommend capturing the arguments into something that holds a configuration and can do whatever it is that needs doing based on that configuration...

Something with an interface like this:

PositionSetter.h:

@interface  PositionSetter : NSObject
{
    NSInteger x;
    NSInteger y;
    Sprite *target;
}

+ positionSetterWithX: (NSInteger) xPos y: (NSInteger) yPos sprite: (Sprite *) aSprite; 

- (void) applyPosition;
@end

PositionSetter.m:

@interface PositionSetter()
@property(readwrite, nonatomic) NSInteger x;
@property(readwrite, nonatomic) NSInteger y;
@property(readwrite, nonatomic, retain) Sprite *target;
@end

@implementation PositionSetter
@synthesize x, y, target;

+ positionSetterWithX: (NSInteger) xPos y: (NSInteger) yPos sprite: (Sprite *) aSprite; 
{
    PositionSetter *positionSetter = [PositionSetter new];
    positionSetter.x = xPos;
    positionSetter.y = yPos;
    positionSetter.target = aSprite;
    return [positionSetter autorelease];
}

- (void) applyPosition;
{
    [self.target setPosition:CGPointMake(self.x,self.y)];
}
@end

Usage is quite straightforward:

positionSetter = [PositionSetter positionSetterWithX: 42 y: 21 sprite: mySprite];
[positionSetter performSelector: @selector(applyPosition) withObject: nil afterDelay: 1.0];

While a tad more code, the resulting implementation will be fast enough -- probably faster than NSInvocation, but fast enough to be irrelevant given that this is gonna cause drawing -- and a heck of a lot more flexible. I could easily see refactoring the above into driving, say, CoreAnimation.

Answer 3

Copied from an answer by Matt Ball:

    - (void)startMyTimer {
        /* ... Some stuff ... */
        NSDictionary *userDict;
        userDict = [NSDictionary dictionaryWithObjectsAndKeys:someValue,
                                                              @"value1",
                                                              someOtherValue,
                                                              @"value2", nil];

        [NSTimer scheduledTimerWithTimeInterval:0.1
                                         target:self
                                       selector:@selector(callMyMethod:)
                                       userInfo:userDict
                                        repeats:YES];
}
    - (void)callMyMethod:(NSTimer *)theTimer {
        NSString *value1 = [[theTimer userInfo] objectForKey:@"value1"];
        NSString *value2 = [[theTimer userInfo] objectForKey:@"value2"];
        [self myMethod:value1 setValue2:value2];
    }

Answer 4

You can pass an NSDictionary*, or some other object, as the userInfo and put the arguments in that.

Answer 5

As an alternative to NSTimer, on iOS 4.0+ and 10.6+, you could use Grand Central Dispatch and dispatch sources to do this using a block. Apple has the following code for this in their Concurrency Programming Guide:

dispatch_source_t CreateDispatchTimer(uint64_t interval, uint64_t leeway, dispatch_queue_t queue, dispatch_block_t block)
{
    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
    if (timer)
    {
        dispatch_source_set_timer(timer, dispatch_walltime(NULL, 0), interval, leeway);
        dispatch_source_set_event_handler(timer, block);
        dispatch_resume(timer);
    }
    return timer;
}

You could then set up a one-second timer event using code like the following:

dispatch_source_t newTimer = CreateDispatchTimer(1ull * NSEC_PER_SEC, (1ull * NSEC_PER_SEC) / 10, dispatch_get_main_queue(), ^{
    [self setX:someValue andY:otherValue andObject:obj];
});

as long as you store and release your timer when done. This can even let you trigger a timer to execute items on a background thread by using a concurrent queue instead of the main queue used above.

This can avoid the need for boxing and unboxing arguments.

Answer 6

Create dictionary with those arguments and pass that dictionary with timer userinfo. That will solve your problem