c struct implementation in iOS

Question

SSharedAppState.h

#import <Foundation/Foundation.h>

enum {
    SharedCompletedStepNone    = 0,
    SharedCompletedStepOne     = 1 << 0,
    SharedCompletedStepTwo      = 2 << 1,
    SharedCompletedStepThree   = 3 << 2
};
typedef NSUInteger SharedCompletedSteps;

@interface SSharedAppState : NSObject
{
    struct {
        unsigned int sharedCompletedStepMask:3;
    } _appFlags;
}
@property (assign, nonatomic) SharedCompletedSteps sharedCompletedStep;

+(id)sharedInstance;
@end

SSharedAppState.m

#import "SSharedAppState.h"

#pragma mark - C functions


#pragma mark - Interface Extension

typedef struct _appFlags AppFlags;
@interface SSharedAppState ()

@property (unsafe_unretained, nonatomic) AppFlags *appFlags;
-(void *)newAppFlags;
@end

#pragma mark - Implementation

@implementation SSharedAppState
@synthesize appFlags;

#pragma mark - Iniitalizer

-(id)init
{
    self = [super init];
    if (self) {

//        appFlags = (AppFlags *)malloc(sizeof(_appFlags));
        appFlags = (AppFlags *)newAppFlags();
        appFlags->sharedCompletedStepMask = 0;
        appFlags.sharedCompletedStepMask = 0;
    }
    return self;
}

+(SSharedAppState *)sharedInstance
{
    static dispatch_once_t onceToken;
    static id sharedInstance;
    dispatch_once(&onceToken, ^{
        sharedInstance = [[self alloc] init];
    });
    return sharedInstance;
}

#pragma makr - Struct _appFlags

-(void *)newAppFlags
{
    AppFlags *instance = (AppFlags *)malloc(sizeof(_appFlags));
    return instance;
}


@end

Questions

appFlags = (AppFlags *)newAppFlags();

gives implicit declaration of function newAppFlags is invalid in C99

appFlags->sharedCompletedStepMask = 0; appFlags.sharedCompletedStepMask = 0;

Incomplete definition of type 'struct _appFlags' Member reference type 'AppFlags *' (aka 'struct _appFlags *') is a pointer; maybe you meant to use '->'?

Gives following warnings and error. These is my first time to post questions here so please advice on html or editing. Thankyou!

AndersK · Accepted Answer · 2012-08-09 06:14:19Z

2

When you write like this

struct {
    unsigned int sharedCompletedStepMask:3;
} _appFlags;

you are declaring a variable _appFlags of an unnamed struct.

you probably meant

struct _appFlags {
    unsigned int sharedCompletedStepMask:3;
};

or you could write

typedef struct _appFlags {
    unsigned int sharedCompletedStepMask:3;
} AppFlags;

answered Aug 9, 2012 at 6:14

AndersK

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2 Comments

neerajgoyal12 Over a year ago

i made the necessary changes but still not able to bind my sharedCompletedStepMask and sharedCompletedStep i am trying to understand why apple would keep similar implementation in UIView or UITableView if for not maintaining a state machine which is what i want to do for my application.

neerajgoyal12 Over a year ago

well can't use typedef in @interface { typedef ... }

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