Passing Data between View Controllers (yes, I know... )

Question

Yes, I know that this question is very popular here and has been given a lot of answers to this question, and yes, I was here Passing Data between View Controllers. But I can't do it for a long time.

in ViewControllerB.h I create a property for the BOOL

@property(nonatomic) BOOL *someBool;

ViewControllerA.m:

#import "ViewControllerB.h"

ViewControllerB *viewControllerB = [[ViewControllerB alloc] init];
viewControllerB.someBool = YES;
[self.navigationController pushViewController:viewControllerB  animated:YES];

In ViewControllerB.m ViewDidLoad:

NSLog(@"%@", self.someBool);

But xCode give me error on this line ( NSLog(@"%@", self.someBool);) and say: Thread 1:EXC_BAD_ACCESS (code =2). What am I doing wrong?

@rokjarc Why are you suggesting that this be moved to a singleton? There is no basis for such a suggestion in this case. — rmaddy, Nov 14 '13 at 17:25
@rmaddy: ok, i admit i'm exaggerating a bit. But this particular case is just a part of the bigger app. I believe there is no place for data in views or controllers. The sooner people learn to use MVC, the less questions on passing data between viewcontrollers will be :) — Rok Jarc, Nov 14 '13 at 17:40
@rokjarc While I agree that proper use of the M in MVC is important, view controllers do have their own state and properties. Not everything belongs in the model. — rmaddy, Nov 14 '13 at 17:48

score 5 · Accepted Answer · answered Nov 14 '13 at 17:09

5

Your property is a pointer. It shouldn't be. Change this:

@property(nonatomic) BOOL *someBool;

to:

@property(nonatomic) BOOL someBool;

The log should be:

NSLog(@"%d", self.someBool);

Only use %@ with objects.

answered Nov 14 '13 at 17:09

rmaddy

314,917
42
532
579

BTW - it is important to understand why and when you use a pointer and why and when you don't. You don't in this case because `BOOL` is a native type and not a class. Except for very rare conditions, when you define a property, never use a pointer for native types and of course you must use a pointer with object types. – rmaddy Nov 14 '13 at 17:51

score 2 · Answer 2 · answered Nov 14 '13 at 17:09

2

Declare it as a BOOL, not a pointer to a BOOL:

@property(nonatomic) BOOL someBool;

answered Nov 14 '13 at 17:09

DrummerB

39,814
12
105
142

score 1 · Answer 3 · answered Nov 14 '13 at 17:11

1

You either need to declare it as a primitive and get rid of the * or store it as an object by wrapping it as an NSNumber

@property (strong, nonatomic) NSNumber *someBool

Then you'd write someBool.boolValue to grab its value

answered Nov 14 '13 at 17:11

Peter Foti

5,526
6
34
47

Passing Data between View Controllers (yes, I know... )

3 Answers3