gistfile1.m

#import "ViewController.h"
#import <AudioToolbox/AudioToolbox.h>

typedef struct{
    float progress;
    float inc;
    BOOL increasing;
}SinStruct;



@implementation ViewController{
    SinStruct sinStruct;
    
    NSSlider *slider;
    NSTextView *sliderFreqLabel;
    NSBox *box;
    float position;
}

- (void)viewDidLoad {

    [super viewDidLoad];
    
    slider = [[NSSlider alloc]initWithFrame:NSRectFromCGRect(CGRectMake(45, 45, 240, 45))];
    slider.maxValue = 1760;
    slider.minValue = 220;
    slider.floatValue = 880;
    
    [slider setTarget:self];
    [slider setAction:@selector(sliderTarget:)];
    
    sliderFreqLabel = [[NSTextView alloc]initWithFrame:NSRectFromCGRect(CGRectMake(45, 90, 240, 45))];
    [sliderFreqLabel setString:[NSString stringWithFormat:@"%f",slider.floatValue]];
    [self.view addSubview:sliderFreqLabel];
    [self.view addSubview:slider];

    
    sinStruct.progress = 0;
    sinStruct.increasing = 1;
    sinStruct.inc = 880 / 44100.0;  //       hz/sample rate
    
    
    
    box = [[NSBox alloc]initWithFrame:NSRectFromCGRect(CGRectMake(0, 100, 100, 100))];
    box.fillColor = [NSColor colorWithRed:1 green:0 blue:0 alpha:1];
    [self.view addSubview:box];
    
    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:1.0 / 60.0 target:self selector:@selector(moveBox) userInfo:nil repeats:1];
    
//    NSTimer *timer = [NSTimer timerWithTimeInterval:1.0 / 60.0 target:self selector:@selector(moveBox) userInfo:nil repeats:1];
//    [[NSRunLoop mainRunLoop]addTimer:timer forMode:NSRunLoopCommonModes];
    
    
    [self performSelector:@selector(setUpAudioUnits) withObject:nil afterDelay:1];
    
}

-(void)moveBox{
    NSRect rect = box.frame;
    rect.origin.x = position;
    box.frame = rect;
}




-(void)sliderTarget:(NSSlider *)slider{
    [sliderFreqLabel setString:[NSString stringWithFormat:@"%f",slider.floatValue]];
    self->sinStruct.inc = slider.floatValue / 44100.0;
}

OSStatus my_callback(	void *							inRefCon,
                     AudioUnitRenderActionFlags *	ioActionFlags,
                     const AudioTimeStamp *			inTimeStamp,
                     UInt32							inBusNumber,
                     UInt32							inNumberFrames,
                     AudioBufferList *				ioData){
    
    ViewController *self = (__bridge ViewController *)inRefCon;
    
    
    self->position++;
    
    float *left = ioData->mBuffers[0].mData;
    float *right = ioData->mBuffers[1].mData;
    
    for (int i = 0; i < inNumberFrames;i++){
        
        if (self->sinStruct.increasing){
            self->sinStruct.progress = self->sinStruct.progress + self->sinStruct.inc;
            
            if (self->sinStruct.progress >= 1.0) {
                self->sinStruct.increasing = 0;
            }
        }
        else{
            self->sinStruct.progress = self->sinStruct.progress - self->sinStruct.inc;
            
            if (self->sinStruct.progress <= -1.0) {
                self->sinStruct.increasing = 1;
            }
        }
        left[i] = sinf((self->sinStruct.progress * (M_PI / 2.0)));
        right[i] = left[i];
    }
    return 0;
}


-(void)setUpAudioUnits{
    AUGraph audioGraph;
    NewAUGraph(&audioGraph);
    
    AUNode ioNode;
    AudioComponentInstance ioUnit;
    
    AudioComponentDescription ioDesc = {0};
    ioDesc.componentFlags = 0;
    ioDesc.componentFlagsMask = 0;
    ioDesc.componentManufacturer = kAudioUnitManufacturer_Apple;
    ioDesc.componentSubType =  kAudioUnitSubType_DefaultOutput;
    ioDesc.componentType    = kAudioUnitType_Output;
    
    AUGraphAddNode(audioGraph, &ioDesc, &ioNode);
    AUGraphOpen(audioGraph);
    AUGraphNodeInfo(audioGraph, ioNode, NULL, &ioUnit);
    
    AURenderCallbackStruct cbStruct = {my_callback, (__bridge void *)self};
    AUGraphSetNodeInputCallback(audioGraph, ioNode, 0, &cbStruct);
    
    AUGraphInitialize(audioGraph);
    AUGraphStart(audioGraph);
    
}






- (void)setRepresentedObject:(id)representedObject {
    [super setRepresentedObject:representedObject];

    // Update the view, if already loaded.
}

@end