Question

I am using Cocoa on Mac 10.6. I am trying to have a metronome click out the time but when I run the code only the first two sounds are played then it is quiet till the end when a sound plays again. If I replace the [player play] statements with NSBeep() it works fine. Any suggestions?

#import <Cocoa/Cocoa.h>


@interface Metronome : NSObject {

NSInteger timeSig;
NSInteger noteValue;
NSInteger bpm;
NSUInteger beatNumber;
CGFloat duration;
NSSound *tickPlayer;
NSSound *tockPlayer;

}
@property(readwrite) NSInteger timeSig;
@property(readwrite) NSInteger noteValue;
@property(readwrite) NSInteger bpm;
@property(readwrite) float duration;
@property(readwrite) NSUInteger beatNumber;

-(id)init;
-(id)initWithTimeSig:(NSInteger)ts  andNoteValue:(NSInteger)nv andBpm:(NSInteger)bp;
-(void)BeginMetronome;
 -(void)PlaySound;

@end

#import "Metronome.h"

 #define defaultBpm 80
 #define defaultTimeSig 4
 #define defaultNoteValue 4

 @implementation Metronome

 @synthesize timeSig, noteValue, duration, bpm, beatNumber;
 -(id)init{
return [self initWithTimeSig:defaultTimeSig andNoteValue:defaultNoteValue       andBpm:defaultBpm];
 }
 -(id)initWithTimeSig:(NSInteger)ts andNoteValue:(NSInteger)nv andBpm:(NSInteger)bp {
[super init];
if(self){
    self.timeSig = ts;
    self.noteValue = nv;
    self.bpm = bp;
    self.duration = 60.0/bpm;
    tickPlayer = [NSSound soundNamed:@"Hat1"];
    tockPlayer = [NSSound soundNamed:@"Hat2"];
    self.beatNumber = 1;


}
return self;
 }
 -(void)BeginMetronome{
BOOL continuePlaying = YES;
NSInteger iter=0;

while (continuePlaying){
    if(iter > 12){
        continuePlaying = FALSE;
    }
    iter++;
    [self PlaySound];
    NSDate *curtainTime = [[NSDate alloc] initWithTimeIntervalSinceNow:self.duration];
    NSDate *currentTime = [[NSDate alloc] init];

    while (continuePlaying && ([currentTime compare:curtainTime] != NSOrderedDescending)) { 
        // if ([soundPlayerThread isCancelled] == YES) {
        //   continuePlaying = NO;
        //}
        //[NSThread sleepForTimeInterval:0.01];
        sleep(.01);
        //[tickPlayer stop];
        //[tockPlayer stop];
        [currentTime release];
        currentTime = [[NSDate alloc] init];
    }
    [curtainTime release];      
    [currentTime release];      

}
}
  - (void)PlaySound {          //***********Problem in this loop
if ([tickPlayer isPlaying])
    [tickPlayer stop];
if ([tockPlayer isPlaying])
    [tockPlayer stop];

if (beatNumber == 1) {
    [tockPlayer play];
}
else if (beatNumber == 2){
    [tickPlayer play];
}
else if (beatNumber == self.timeSig) {
    beatNumber = 0;
    [tickPlayer play];
}
else{
    //[tickPlayer stop];
    [tickPlayer play];
    NSBeep();
}


beatNumber++;
//NSLog(@" %d ", beatNumber);
 // NSBeep();
 }



 @end

Answer 1

I believe your use of sleep() is blocking the playing of NSSound. That’s a very sloppy way to do this, instead use a timer like so:

static NSInteger iter;

- (void) beginMetronome {

    iter = 0;

    NSTimer *timer = [NSTimer timerWithTimeInterval:self.duration target:self selector:@selector(continueMetronome:) userInfo:nil repeats:YES];
    [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
    [timer fire];    
}

- (void) continueMetronome:(NSTimer *)theTimer {

    [self PlaySound];

    if (++iter > 12) {

        [theTimer invalidate];
    }
}

Also, you must retain the sounds that you plan to use in your init method.

tickPlayer = [[NSSound soundNamed:@"Hat1"] retain];
tockPlayer = [[NSSound soundNamed:@"Hat2"] retain];

And Cocoa methods should start with a lowercase letter like I’ve written them. I’m not too sure how metronomes are supposed to work, so you may have to change the value of 12 to something else.