Thread-safe NSObject array iteration/enumeration

button_array.h

#import <objc/runtime.h>

static __strong id _Nonnull buttons[5];
static __strong const id * _Nonnull (*buttons_t)[5] = &buttons;

static void (^(^map)(id * _Nonnull, const unsigned long))(const void *(^__strong)(const unsigned long)) = ^ (id * _Nonnull obj_collection, const unsigned long index_count) {
    __block unsigned long (^recursive_block)(unsigned long);
    return ^ (const void * (^enumeration)(const unsigned long)) {
        (recursive_block = ^ unsigned long (unsigned long counter) {
            obj_collection[counter] = (__bridge id)((__bridge const void * _Nonnull)CFBridgingRelease(enumeration(counter)));
            return (unsigned long)((counter += 1) ^ index_count) && (unsigned long)(recursive_block)(counter);
        })(0ul);
    };
};

/*

Older versions (non-recursive) below

*/

static __strong UIButton * _Nonnull buttons[5];
static void (^(^populate_collection)(__strong UIButton * _Nonnull [_Nonnull 5]))(UIButton * (^__strong)(unsigned int)) = ^ (__strong UIButton * _Nonnull button_collection[5]) {
    dispatch_queue_t enumerator_queue  = dispatch_queue_create("enumerator_queue", DISPATCH_QUEUE_SERIAL);
    return ^ (UIButton *(^enumeration)(unsigned int)) {
        dispatch_apply(5, enumerator_queue, ^(size_t index) {
            dispatch_barrier_async(dispatch_get_main_queue(), ^{
                button_collection[index] = enumeration((unsigned int)index);
            });
        });
    };
};

static void (^(^enumerate_collection)(__strong UIButton * _Nonnull [_Nonnull 5]))(void (^__strong)(UIButton * _Nonnull, unsigned int)) = ^ (__strong UIButton * _Nonnull button_collection[5]) {
    dispatch_queue_t enumerator_queue  = dispatch_queue_create("enumerator_queue", DISPATCH_QUEUE_SERIAL);
    return ^ (void(^enumeration)(UIButton * _Nonnull, unsigned int)) {
        dispatch_barrier_async(dispatch_get_main_queue(), ^{
        dispatch_apply(5, enumerator_queue, ^(size_t index) {
        for (int index = 0; index < 5; index++)
            dispatch_barrier_async(dispatch_get_main_queue(), ^{
                enumeration(button_collection[index], (unsigned int)index); // no return value
            });
        });
        });
    };
};

button_array.m

map(&buttons, 5)(^ const void * (const unsigned long index) {
        printf("map button %lu\n", index);
        __block UIButton * button;
        [button = [UIButton new] setTag:index];
        [button setImage:[UIImage systemImageNamed:CaptureDeviceConfigurationControlPropertyImageValues[0][index] withConfiguration:CaptureDeviceConfigurationControlPropertySymbolImageConfiguration(CaptureDeviceConfigurationControlStateDeselected)] forState:UIControlStateNormal];
        [button setImage:[UIImage systemImageNamed:CaptureDeviceConfigurationControlPropertyImageValues[1][index] withConfiguration:CaptureDeviceConfigurationControlPropertySymbolImageConfiguration(CaptureDeviceConfigurationControlStateSelected)] forState:UIControlStateSelected];
        [button setImage:[UIImage systemImageNamed:CaptureDeviceConfigurationControlPropertyImageValues[1][index] withConfiguration:CaptureDeviceConfigurationControlPropertySymbolImageConfiguration(CaptureDeviceConfigurationControlStateHighlighted)] forState:UIControlStateHighlighted];
        NSMutableParagraphStyle *centerAlignedParagraphStyle = [[NSMutableParagraphStyle alloc] init];
        centerAlignedParagraphStyle.alignment = NSTextAlignmentCenter;
        NSDictionary *centerAlignedTextAttributes = @{NSForegroundColorAttributeName:[UIColor systemYellowColor],
                                                      NSFontAttributeName:[UIFont systemFontOfSize:14.0],
                                                      NSParagraphStyleAttributeName:centerAlignedParagraphStyle};
        
        NSString *valueString = [NSString stringWithFormat:@"%.2f", 0.00];
        NSAttributedString *attributedString = [[NSAttributedString alloc] initWithString:valueString attributes:centerAlignedTextAttributes];
        [button setAttributedTitle:attributedString forState:UIControlStateNormal];
        [button.titleLabel setFrame:UIScreen.mainScreen.bounds];
        [button sizeToFit];
        
        float angle = rescale(index, 0.0, 4.0, 180.0, 270.0);
        NSNumber * button_angle = [NSNumber numberWithFloat:angle];
        objc_setAssociatedObject (button,
                                  (void *)index,
                                  button_angle,
                                  OBJC_ASSOCIATION_RETAIN);
        
        [button setUserInteractionEnabled:FALSE];
        void (^eventHandlerBlockTouchUpInside)(void) = ^{
            NSNumber * associatedObject = (NSNumber *)objc_getAssociatedObject (button, (void *)index);
            //            printf("%s\n", [[associatedObject stringValue] UTF8String]);
        };
        objc_setAssociatedObject(button, @selector(invoke), eventHandlerBlockTouchUpInside, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
        [button addTarget:eventHandlerBlockTouchUpInside action:@selector(invoke) forControlEvents:UIControlEventTouchUpInside];
        
        CGPoint target_center = point_from_angle(angle);
        [button setCenter:target_center];
        [self addSubview:button];
        
        return (const id *)CFBridgingRetain(button);
    });

/*

Older versions (non-recursive) below

*/

populate_collection(buttons)(^ UIButton * (unsigned int index) {
        UIButton * button;
        [button = [UIButton new] setTag:index];
        [button setImage:[UIImage systemImageNamed:@"questionmark.circle" withConfiguration:[[UIImageSymbolConfiguration configurationWithPointSize:42] configurationByApplyingConfiguration:[UIImageSymbolConfiguration configurationPreferringMulticolor]]] forState:UIControlStateNormal];
        [button sizeToFit];
        void (^eventHandlerBlock)(void) = ^{ };
        objc_setAssociatedObject(button, @selector(invoke), eventHandlerBlock, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
        [button addTarget:eventHandlerBlock action:@selector(invoke) forControlEvents:UIControlEventTouchUpInside];
        [self.view addSubview:button];
        float angle = 270.0 - ((90.0 / 4.0) * button.tag);
        [button setCenter:[[UIBezierPath bezierPathWithArcCenter:CGPointMake(CGRectGetMaxX(self.view.bounds), CGRectGetMaxY(self.view.bounds)) radius:CGRectGetMidX(self.view.bounds) startAngle:degreesToRadians(angle) endAngle:degreesToRadians(angle) clockwise:FALSE] currentPoint]];
        return button;
    });
    
    enumerate_collection(buttons)(^ (UIButton * _Nonnull button, unsigned int property) {
        float angle = 270.0 - ((90.0 / 4.0) * button.tag);
        [button setCenter:[[UIBezierPath bezierPathWithArcCenter:CGPointMake(CGRectGetMidX(self.view.bounds), CGRectGetMidY(self.view.bounds)) radius:CGRectGetMidX(self.view.bounds) startAngle:degreesToRadians(angle) endAngle:degreesToRadians(angle) clockwise:FALSE] currentPoint]];
    });