objective-c - 如何将回调对象从 Wwift 传递到 Objective C 类并用作回调？

Question

我正在尝试使用 Objective C 中的回调来回调到 Swift 类。我的实现有效，但是我试图将“self.callback(val)”回调移动到我的 AudioCallback 函数。我怎样才能做到这一点？

我尝试在我的目标 c 类中创建一个全局变量，但不确定要使用什么类型，或者这是否是最佳实践。关于如何完成此任务的任何想法？

这是我的标题：

#import <Foundation/Foundation.h>

@interface Listener : NSObject

-(id)init;
- (void) startListner;

@property (nonatomic, copy) void(^callback)(Float32);

@end

这是我的目标c实现

#pragma mark MAIN CALLBACK
static void AudioCallback( Float32 * buffer, UInt32 frameSize, void * userData )
{
    
    
    //take only data from 1 channel
    Float32 zero = 0.0;
    vDSP_vsadd(buffer, 2, &zero, buffer, 1, frameSize*NUMCHANNELS);
    
    
    
    if (accumulateFrames(buffer, frameSize)==YES) { //if full
        
        //windowing the time domain data before FFT (using Blackman Window)
        if (windowBuffer==NULL) { windowBuffer = (Float32*) malloc(sizeof(Float32)*windowLength); }
        vDSP_blkman_window(windowBuffer, windowLength, 0);
        vDSP_vmul(dataAccumulator, 1, windowBuffer, 1, dataAccumulator, 1, accumulatorDataLenght);
        //=========================================
        
        
        Float32 maxHZValue = 0;
        Float32 maxHZ = strongestFrequencyHZ(dataAccumulator, fftConverter, accumulatorDataLenght, &maxHZValue);
        
        NSLog(@" max HZ = %0.3f ", maxHZ);
        dispatch_async(dispatch_get_main_queue(), ^{ //update UI only on main thread
            //labelToUpdate.text = [NSString stringWithFormat:@"%0.3f HZ",maxHZ];
            //printf("{}", [NSString stringWithFormat:@"%0.3f HZ",maxHZ]);
            NSLog(@"Value of hello = %@", [NSString stringWithFormat:@"%0.3f HZ",maxHZ]);

            // call here
            self.callback(maxHz);
        });
        
        emptyAccumulator(); //empty the accumulator when finished
    }
    memset(buffer, 0, sizeof(Float32)*frameSize*NUMCHANNELS);
}

@implementation Listener

-(id)init { return self; }

- (void) startListner{
    NSLog(@"SomeMethod Ran");
    //labelToUpdate = HZValueLabel;
    
    //initialize stuff
    fftConverter = FFTHelperCreate(accumulatorDataLenght);
    initializeAccumulator();
    
    bool result = false;
    result = MoAudio::init( SAMPLE_RATE, FRAMESIZE, NUMCHANNELS, false);
    if (!result) { NSLog(@" MoAudio init ERROR"); }
    result = MoAudio::start( AudioCallback, NULL);
    
    if (!result) { NSLog(@" MoAudio start ERROR"); }
    
    self.callback(0.2)
}

@end

标签： objective-cswiftbridging-header

Answer 1

答案是移动@implementation Listener到我班级的顶部，然后设置一个指向我的调用班级的指针：

...
@implementation Listener
Listener *mListener;
...

而在init方法中，将监听器指针指向self：

...
-(id)init {    
    mListener = self;
    return self;
}
...

最后，我可以使用 Listener 指针通过以下方式调用回调：

mListener.Callback(maxHZ);

希望这可以帮助任何像我一样困惑的人。