Question

Need help with a problem.

Goal
I’m putting together an iOS book app that uses NSTimers to fire off several staggered animation events after loading a view. I’ve created a MethodCallerWithTimer class to help me do this (code at bottom).

My Solution So Far
When I use the MethodCallerWithTimer class, I assign the objectOwningMethod as my UIViewController subclass object (it’s a book page), and then the method as an instance method in that class. Here is an example of a method I assign – quite simply turning on some artwork on the screen:

- (void) playEmory {
   [emoryRedArt setHidden:NO];
}

My Issue
When I create multiple MethodCallerWithTimer instances then load the view and start them all, I only ever get the FIRST event to happen. None of the other timers call their target methods. I suspect I don’t understand what I’m asking NSRunLoop to do or something similar.

Any thoughts?

Here is my MethodCallerWithTimer class:

@interface MethodCallerWithTimer : NSObject {
    NSTimer * timer;
    NSInvocation * methodInvocationObject;
    NSNumber * timeLengthInMS;
}

- (id) initWithObject: (id) objectOwningMethod AndMethodToCall: (SEL) method;
- (void) setTime: (int) milliseconds;
- (void) startTimer;
- (void) cancelTimer;

@end

And implementation:

#import "MethodCallerWithTimer.h"

@implementation MethodCallerWithTimer

- (id) initWithObject: (id) objectOwningMethod AndMethodToCall: (SEL) method {
    NSMethodSignature * methSig = [[objectOwningMethod class] instanceMethodSignatureForSelector:method];
    methodInvocationObject = [NSInvocation invocationWithMethodSignature:methSig];
    [methodInvocationObject setTarget:objectOwningMethod];
    [methodInvocationObject setSelector:method];
    [methSig release];
    return [super init];
}
- (void) setTime: (int) milliseconds {
    timeLengthInMS = [[NSNumber alloc] initWithInt:milliseconds];
}
- (void) startTimer {
    timer = [NSTimer scheduledTimerWithTimeInterval:([timeLengthInMS longValue]*0.001) invocation:methodInvocationObject repeats:NO];
}
- (void) cancelTimer {
    [timer invalidate];
}
-(void) dealloc {
    [timer release];
    [methodInvocationObject release];
    [timeLengthInMS release];
    [super dealloc];
}

@end

Answer 1

These look like one-time firings after a delay; have you considered using something like:

[myObject performSelector:@selector(playEmory) withObject:nil afterDelay:myDelay];

where myObject is the instance with the playEmory routine and myDelay is a float of the seconds you want the OS to wait before making the call?

You can find out more information about this flavor of performSelector here.