In ObjectiveC using delegate how do I send a message without using a UIButton?

问题

I recently learned to use delegates to send messages from one class to another whenever a button is pressed and I'd like to find out how to send a message without a button action. Apple documentation suggests a likely method is performSelector:(SEL)aSelector; but I had no luck when I tried to use it. Instead, this is what I tried.

In MicroTune.h, I defined a delegate and gave it a property

    @class Synth;

    @protocol TuningDelegate <NSObject>
        -(void)setTuning:(NSData *)tuningData;
    @end

    @interface MicroTune : NSObject
        {
        …
        }

    @property (assign) id<TuningDelegate> delegate;
    @end

In Synth.h, I declared the class so it acts as a delegate

    #import "MicroTune.h"

    @interface Synth : NSObject <TuningDelegate>

and in Synth.m, I created a method to let me know the message arrived

    #import "Synth.h"

    - (void)setTuning:(NSData *)tuningData
    {
        NSArray *array = [NSKeyedUnarchiver unarchiveObjectWithData:tuningData];
        NSLog(@" hip hip %@", array);
    }

EDIT

And, also in Synth.m, to make sure the delegate is recognised, I added the following

    - (id)initWithSampleRate:(float)sampleRate_ 
        { if ((self = [super init])) 
            { 
                microTuneClassObject.delegate = self;

                // etc. etc.

            } return self; 
        }
                    (Use of undeclared identifier 'microTuneClassObject')

and also tried

    MicroTune.delegate = self;
        (Property 'delegate' not found on object of type 'MicroTune')

and

    self.MicroTune.delegate = self;
        (Property 'MicroTune' not found on object of type 'Synth *')

And finally, in MicroTune.m, I defined a method to send the message

    #import "MicroTune.h"

    - (void)sendTuning:(NSData *)tuningData 
    {
        [synthLock lock];
        [self.delegate setTuning:(NSData *)tuningData];
        [synthLock unlock];
    }

but Xcode gave the following message.

      No type or protocol named 'TuningDelegate'

Can someone kindly explain what I need to do to send the message ? Thanks.

CONCLUSION

The solution can be found in my supplementary answer.

回答1:

In MicroTune.h file,

instead of #import "Synth.h" write @class Synth

回答2:

In Synth.h

    @class MicroTune;

    @interface Synth : NSObject
    {
        MicroTune      *setTuning;
    }

    - (MicroTune*)setTuning;

In Synth.m

    #import "Synth.h"
    #import "MicroTune.h"

and from Synth.m, tuning data is retrieved from MicroTune (when the PlayViewController sends a MIDI Program Change message)

    - (void)sendProgramChange:(uint8_t)oneOfFiveFamilies
            onChannel:(uint8_t)oneOfSixteenPlayers
    {
        uint8_t tuningTransposition     = oneOfFiveFamilies;
        uint8_t assignedPitches         = oneOfSixteenPlayers;

        MicroTune *dekany               = [[MicroTune alloc] init];

    // send a 2-byte "MIDI event" to fetch archived tuning data

        id archivedArray                = [dekany sendMIDIEvent:(uint8_t)tuningTransposition
                                                  data1:(uint8_t)assignedPitches];

        NSArray *array                  = [NSKeyedUnarchiver unarchiveObjectWithData:archivedArray];

        NSLog(@"\n%@", array);

        for (int i = 0; i <10; i++)
        {
            NSNumber *num               = array[i];
            float hertz                 = [num floatValue];
            _pitches[i]                 = hertz;
        }
    }

来源：https://stackoverflow.com/questions/44969276/in-objectivec-using-delegate-how-do-i-send-a-message-without-using-a-uibutton

标签

ios

objective-c

delegates

selector