Cannot access NSMutableDictionary from another class

Question

I'm new to Objective C and I'm having a problem reading NSMutableDisctionary from another class. NSMutableDictionary itself is working fine in ViewController class, but when I try to read it in TestResults class i get empty dictionary. Where did I go wrong? Thanks!

ViewController.h

@property NSMutableDictionary *storedAnswers;

ViewController.m

@implementation ViewController
@synthesize questionScrollView;
- (id)init
{
    self = [super init];
    if (self) {
        [_storedAnswers setObject:@"aaa" forKey:@"bbb"];
    }
    return self;
}

TestResults.h

#import "ViewController.h"

ViewController *answers = [[ViewController alloc] init];
NSLog(@"%@",answers.storedAnswers);

This is a dupe a thousand times over. – Hot Licks Mar 14 '14 at 22:20 — Hot Licks, Mar 14 '14 at 22:20

score 2 · Answer 1 · answered Mar 14 '14 at 22:09

2

You're accessing the dictionary just fine. You're not accessing the correct ViewController instance though. You need to get a reference to the view controller--not just instantiate another instance of the view controller.

answered Mar 14 '14 at 22:09

nhgrif

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Would you be able to give an example of code how to do this please? – Domas Mar 14 '14 at 22:13
Any tutorial any where will show you how to pass data from view controllers. – nhgrif Mar 14 '14 at 22:15

score 0 · Answer 2 · answered Mar 14 '14 at 22:10

0

What makes you think that _storedAnswers would be anything other than nil?

answered Mar 14 '14 at 22:10

gnasher729

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more of a recrimination that an answer – Grady Player Mar 14 '14 at 22:13

score 0 · Answer 3 · answered Mar 14 '14 at 22:10

0

_storedAnswers is never initialized (that we can see here). Add:

_storedAnswers = [NSMutableDictionary new];

before you start using it.

answered Mar 14 '14 at 22:10

David Berry

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this could do the job, as it passes data to another class but then i have to add some more data to this dictionary and it wont happen... – Domas Mar 14 '14 at 22:18

score 0 · Answer 4 · answered Mar 14 '14 at 22:39

0

ViewController.h

@property NSMutableDictionary *storedAnswers;

ViewController.m

@implementation ViewController
@synthesize questionScrollView;
- (id)init
{
    self = [super init];
    if (self) {
        _storedAnswers = [NSMutableDictionary alloc] init];
        [_storedAnswers setObject:@"aaa" forKey:@"bbb"];
    }
    return self;
}

- (void) dealloc
{
    _storedAnswers = nil; // free memory if ARC is enable
}

answered Mar 14 '14 at 22:39

Khalil

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15

this passes the data. but what about if i want to add more data to this dictionary outside this method in ViewController.m ? – Domas Mar 14 '14 at 22:45
ViewController *answer = [[ViewController alloc] init]; [answer.storedAnswer setObject:@"secondObject" forKey:@"secondKey"]; – Khalil Mar 14 '14 at 22:51
so i would you use this in a second class. what about adding some more data in a class where that dictionary originally is? – Domas Mar 14 '14 at 23:03
Domas, can you more explain? – Khalil Mar 14 '14 at 23:10
Right.. Your given answer technically works. It's a method that creates NSMutableDictionary and adds some data in it. That's fine. But then later in a same class I have more methods where I want to put more data in to the same dictionary. And in the end, i want to read all that data in another class.. hope you understood me – Domas Mar 14 '14 at 23:15
if you want read data from dictionary use this: [_answerStored ObjectForKey:@"secondKey"]; this return value of key; and if you want get all keys or value you can use [_storedAnswer allKeys] or [_storedAnswer allValues]; // sorry for my bad english – Khalil Mar 14 '14 at 23:24
ok, but i want to insert more data, not read – Domas Mar 14 '14 at 23:26
[_storedAnswers setObject:@"bbb" forKey:@"Key1"]; [_storedAnswers setObject:@"bbb" forKey:@"Key2"]; [_storedAnswers setObject:@"bbb" forKey:@"Key3"]; and more ? what is this? – Khalil Mar 14 '14 at 23:27
but if i use this line of code in different methods that doesn't work and this is a problem.. – Domas Mar 14 '14 at 23:29
no, the data is just not added.. i guess i need to read some tutorials.. – Domas Mar 14 '14 at 23:34

Cannot access NSMutableDictionary from another class

4 Answers4