How to use a run loop with NSTimer in Objective-C - objective-c

Question

I am writing a small program for printing to the console every few seconds.
The objective is to call a function on each of ten objects in an array every N seconds, where n is a class variable. I was wondering how I could incorporate such a timer loop into my code. Here is what I have. I would ver much appreciate a response. Thanks.
ALHuman.m
static NSInteger barkInterval = 3;
#implementation ALHuman
-(void)setMyDog:(ALDog *)dog{
myDog = dog;
}
-(ALDog *)getMyDog{
return myDog;
}
+(NSInteger)returnBarkInterval {
return barkInterval;
}
-(void)createDog{
ALDog *aDog = [[ALDog alloc]init];
char dogName [40] = " ";
NSLog(#"Please enter a name for %s's dog",[self name]);
scanf("%s",dogName);
[aDog setName:dogName];
char barkSound [40] = "";
NSLog(#"Please enter a bark sound for dog: %s",[aDog name]);
scanf("%s",barkSound);
[myDog setBarkSound:barkSound];
[myDog setCanBark:YES];
[self setMyDog:aDog];
}
-(void)callDog:(NSInteger)numberOfResponses {
NSLog(#"%s",[[self getMyDog] name]);
[[self getMyDog] bark:numberOfResponses];
}
-(NSInteger)getRandomNumberBetween:(NSInteger)from to:(NSInteger)to {
return (NSInteger)from + arc4random() % (to-from+1);
}
-(void)timerFireMethod:(NSTimer *)timer {
[self callDog:[self getRandomNumberBetween:1 to:5]];
}
#end
main.m
int main(int argc, const char * argv[])
{
#autoreleasepool {
NSMutableArray *people = [[NSMutableArray alloc]init];
for (int i = 0; i < 10; i++) { // I didn't want to create a class method for creating these humans and their dogs, because it is unneccessary.
ALHuman *person = [[ALHuman alloc]init];
// NameGenerator *name = [[NameGenerator alloc]init]; I need to work on implementing this
[person setName:"Bob"];
[person createDog];
[person setHeight:[person getRandomNumberBetween:5 to:8]];
[people addObject:person];
}
NSLog(#"%#",people);
NSRunLoop* myRunLoop = [NSRunLoop currentRunLoop]; //Here is where I am having trouble
for(ALHuman *human in people){
[NSTimer timerWithTimeInterval:[ALHuman returnBarkInterval] target:human selector:#selector(timerFireMethod:) userInfo:NULL repeats:YES];
}
return 0;
}
}

Answer 1

First, +[NSTimer timerWithTimeInterval:...] creates and returns a new timer object, but you're ignoring the return value. So, those timer objects are just lost and useless. You either want to manually schedule them into the run loop or use +scheduledTimerWithTimeInterval:... instead.
Second, you allow execution to flow to the return statement, which exits the main() function. When that happens, the process is terminated. It doesn't bother waiting for any timers to fire, or anything else for that matter.
If you want to wait and allow those timers to fire, you need to manually run the run loop (since you're not in the main thread of an application, which would run the run loop for you). You can invoke [myRunLoop run], [myRunLoop runUntilDate:someDate], or build a loop around an invocation of [myRunLoop runMode:someMode beforeDate:someDate]. It depends on under what circumstances you want the program to exit, if ever.

Answer 2

Use this simple runloop controller class.
(untested):
int main(int argc, const char * argv[])
{
#autoreleasepool {
RunLoopController *runLoopController = [RunLoopController new];
[runLoopController register];
NSMutableArray *people = [NSMutableArray new];
NSMutableArray *timers = [NSMutableArray new];
for (int i = 0; i < 10; i++) {
ALHuman *person = [[ALHuman alloc]init];
// NameGenerator *name = [[NameGenerator alloc]init]; I need to work on implementing this
[person setName:"Bob"];
[person createDog];
[person setHeight:[person getRandomNumberBetween:5 to:8]];
[people addObject:person];
NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:[ALHuman returnBarkInterval]
target:person
selector:#selector(timerFireMethod:)
userInfo:nil
repeats:YES];
[timers addObject:timer];
}
NSLog(#"%#",people);
while ([runLoopController run])
;
[runLoopController deregister];
}
}
However the issue you face is how to terminate the program when you are finished. You can either install a signal handler, or use some other metric to determine the program has finished, and then call [[RunLoopController mainRunLoopController] terminate].
The RunLoopController uses a simple signalling mechanism (a MACH port) in order to know that the runloop must terminate. Other usage examples exist on the github repo in the above link.