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 timer.

[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector() userInfo:nil repeats:NO];

What to set Here?

How to Pass arguments? (as per my knowledge - selector specifies only the method to invoke)

Answer 1

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

Answer 2

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 3

If you use a target-action timer, you can't have the timer directly call an arbitrary method. A timer's action must have a very specific signature. You can pass additional data in the userinfo dictionary and have the timer's action call the method you ultimately want, or you can use the invocation form as Dave said. Personally, I usually do the former, because I find NSInvocations to be annoying and setting one up can actually take more code than just writing an intermediary method.

Answer 4

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 5

- (void)startMyTimer {
    /* ... Some stuff ... */
    [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(callMyMethod:) userInfo:[NSDictionary dictionaryWithObjectsAndKeys:someValue, @"value1", someOtherValue, @"value2", nil] repeats:YES];
}
- (void)callMyMethod:(NSTimer *)theTimer {
    NSString *value1 = [[theTimer userInfo] objectForKey:@"value1"];
    NSString *value2 = [[theTimer userInfo] objectForKey:@"value2"];
    [self myMethod:value1 setValue2:value2];    
}