Member reference base type 'Class' is not a structure or union - has the Fixit led me in the right direction?

Question

I’m trying to make a delegate that will send messages from UIButtons within a custom UIView called SGView and am a bit out of my depth following the error messages. I recently learned how to get a delegate to send messages successfully from within an instance method.

SGView includes a class method that arranges multiple UIButtonsin a circle and was designed to be used by different UIViews. The geometry works when the method is called from a parent UIView. I have now declared the delegate by adding @protocol and @property to the class method declaration

like so ...

SGView.h

#import <UIKit/UIKit.h>

@protocol SGViewDelegate <NSObject>
    -(void)buttonPressed:(UIButton*)button;
@end

@interface SGView : UIView {
    }
    +(id)circleOfButtons:(int)buttonCount buttonSize:(CGFloat)buttonSize circleRadius:(CGFloat)circleRadius;

@property (assign) id<SGViewDelegate> delegate;

@end

SGView.m is essentially like this

#import "SGView.h"

    @implementation SGView : UIView

    +(id)circleOfButtons:(int)buttonCount buttonSize:(CGFloat)buttonSize circleRadius:(CGFloat)circleRadius
    {
    UIView *multipleViews       = [self new];

    // … circular geometry …

    [circleButton addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside];

    [multipleViews addSubview:circleButton];
    }
    return multipleViews;
    }
    @end

The moment I change the target from self to self.delegate in the target action statement above, Xcode reports three errors

Definition of 'objc_class' must be imported from module 'ObjectiveC.runtime' before it is required

No member named 'delegate' in 'struct objc_class'

Member reference type 'struct objc_class *' is a pointer; did you mean to use '->'?

Xcode offers a Fixit for the last of these

    Fixit Replace”.” with “->”

By accepting the Fixit I removed the three issues and introduced another

Member reference base type 'Class' is not a structure or union

If this Fixit has lead me in the right direction, what exactly should I be doing next ?

I need to ask this question to make sense of what might seem a straight forward problem before diving back into the Apple documentation and these tutorials trying to solve it. Any help is most appreciated. Thanks.

SOLUTION

This can be found in my answer to my own question.

Answer 1

Changing the class method to an instance method appears to have solved my problem.

This involved making the class method +(id)circleOfButtons:... etc into an instance method (-(id)circleOfButtons:... etc) in both .m and .h files. It was also necessary to change the call in the parent UIView from

    SGView *sgView              = [SGView circleOfButtons:count buttonSize:size circleRadius:radius];

to

    SGView *sgView              = [[SGView alloc] circleOfButtons:count buttonSize:size circleRadius:radius];

and change the declaration in SGView from

    UIView *multipleViews       = [self new];

to

    UIView *multipleViews       = [[UIView alloc]initWithFrame:[UIScreen mainScreen].bounds];

SGView can be now reused from different UIViews that change the number and size of UIButtons arranged in a circle. The delegate in SGView also allows each button to send a tagged message to a method in another class - in my case the ViewController.

The complete listing is included below and I'd welcome suggestions or improvements from others with more experience in OO programming.

ViewController.h

#import <UIKit/UIKit.h>

    @interface ViewController : UIViewController <UIContentContainer> {
    }
@end

ViewController.m

#import "ViewController.h"
#import "FamilyView.h"

@interface ViewController ()

@end

@implementation ViewController

    - (void)viewDidLoad                                             {
    [super viewDidLoad];

    NSLog(@"load FamilyView");

    CGRect rect             = [UIScreen mainScreen].bounds;
    float  statusBarHeight  = [[UIApplication sharedApplication] statusBarFrame].size.height;
    CGRect screenFrame      = CGRectMake(0, statusBarHeight, rect.size.width, rect.size.height - statusBarHeight);
    self.view               = [[UIView alloc] initWithFrame: screenFrame];

    FamilyView *cv          = [[FamilyView alloc]initWithFrame:screenFrame];
    [self.view addSubview:cv];    
}


    - (void)buttonPressed:(UIButton*)button                          {
    NSLog(@"Button %ld clicked.", (long int)[button tag]);

    switch (button.tag) {
        case 1:
        //            [self goToFamily1];
            break;
        case 2:
        //            [self goToFamily2];
            break;
        case 3:
        //            [self goToFamily3];
            break;
        case 4:
        //            [self goToFamily4];
            break;
        case 5:
        //            [self goToFamily5];
            break;
        default:
        //            [self goToHelp];
            break;
        }
    }
    @end

FamilyView.h

#import <UIKit/UIKit.h>
#import "ViewController.h"
#import "SGView.h"

    @interface FamilyView : UIView {
    }
@end

FamilyView.m

#import <UIKit/UIKit.h>
#import "FamilyView.h"
#import "SGView.h"

    @implementation FamilyView : UIView

    - (id)initWithFrame:(CGRect)frame {
    self                                    = [super initWithFrame:[UIScreen mainScreen].bounds];
    if (self) {

    self.backgroundColor                    = [UIColor lightGrayColor];

    int     count                           = 5;  //16;
    CGFloat size                            = 80; //41;
    CGFloat radius                          = 68; //105;

    SGView *sgView                          = [[SGView alloc] circleOfButtons:count buttonSize:size circleRadius:radius];
    [self addSubview:sgView];
    }
    return self;
}
@end

SGView.h

#import <UIKit/UIKit.h>

    @protocol SGViewDelegate <NSObject>
    -(void)buttonPressed:(UIButton*)button;
    @end

    @interface SGView : UIView {
    }

      -(id)circleOfButtons:(int)buttonCount buttonSize:(CGFloat)buttonSize circleRadius:(CGFloat)circleRadius;

    @property (assign) id<SGViewDelegate> delegate;

    @end

SGView.m

#import "SGView.h"

    @implementation SGView : UIView

    -(id)circleOfButtons:(int)buttonCount buttonSize:(CGFloat)buttonSize circleRadius:(CGFloat)circleRadius
    {
    UIView *multipleViews                   = [[UIView alloc]initWithFrame:[UIScreen mainScreen].bounds];

    CGPoint screenCentre;
    CGPoint buttonCentre;

    screenCentre.x                          = CGRectGetWidth  ([UIScreen mainScreen].bounds) / 2;
    screenCentre.y                          = CGRectGetHeight ([UIScreen mainScreen].bounds) / 2;

    for (int i = 1; i <= buttonCount; i++) {
        CGFloat radians                     = 2 * M_PI * i / buttonCount;
        CGFloat arcStartPoint               = - M_PI / 2; // first point clockwise after 12 o'clock
        buttonCentre.x                      = screenCentre.x + circleRadius * cos(radians + arcStartPoint);
        buttonCentre.y                      = screenCentre.y + circleRadius * sin(radians + arcStartPoint);

        CGPoint target                      = CGPointMake(buttonCentre.x, buttonCentre.y);
        CGFloat x                           = screenCentre.x - buttonSize / 2;
        CGFloat y                           = screenCentre.y - buttonSize / 2;
        CGFloat wide                        = buttonSize;
        CGFloat high                        = buttonSize;
        UIButton *circleButton              = [[UIButton alloc] initWithFrame:CGRectMake(x, y, wide, high)];

        [circleButton setTag:i];
        [circleButton addTarget:self.delegate action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside];

        circleButton.clipsToBounds          = YES;
        circleButton.layer.masksToBounds    = NO;
        circleButton.layer.shadowOffset     = CGSizeMake(-15, 20);
        circleButton.layer.shadowRadius     = 5;
        circleButton.layer.shadowOpacity    = 0.0;
        circleButton.layer.borderWidth      = 0.25f;
        circleButton.layer.cornerRadius     = buttonSize/2;
        circleButton.layer.borderColor      = [UIColor blackColor].CGColor;
        circleButton.backgroundColor        = UIColor.whiteColor;
        [circleButton setTitle:[NSString stringWithFormat:@"%i", i] forState:UIControlStateNormal];

        if (buttonCount > 25) {
            [circleButton setTitleColor: [UIColor clearColor] forState:UIControlStateNormal];
            } else {
            [circleButton setTitleColor: [UIColor grayColor] forState:UIControlStateNormal];
        }

        [multipleViews addSubview:circleButton];

    // animation 1
        [UIView animateWithDuration:0.5 animations:^{
        circleButton.transform              = CGAffineTransformMakeScale(1.0, 1.0);
        circleButton.center                 = screenCentre;
        }
                     completion:^(BOOL finished){}];

    // animation 2
        [UIView animateWithDuration:0.5f animations:^{
        circleButton.transform              = CGAffineTransformIdentity;
        circleButton.center                 = target;
        }
                     completion:^(BOOL finished){}];
    }
    return multipleViews;
}
@end