如何在不复制项目的情况下更新NSMutableDictionary中对象的值

Question

Apologies if this question is very similar to one I asked previously . However, I am having a new issue I did not encounter previously.

So, I have a bunch of UISwitch elements that are dynamically created based on values (labels and ID numbers) that are stored in a plist. I basically read the plist file and get an array of the items and for each one create the UISwitch. This part is all working great.

The ultimate intent is for the user to be able to make selections with UISwitch and keep track of the value of those switch selections and then save them to Core Data.

This is almost working perfectly, except whenever the user interacts with a switch, it adds a completely new object and key to the NSMutableDictionary

Here is a block of my code I use to build the UI and update the NSMutableDictionary.

.h

@property int yPosStart;
@property NSString *switchValue;
@property (nonatomic, strong) UISwitch *qualifierSwitch;
@property (nonatomic, strong) NSMutableDictionary *evqValuesDict;

.m

for (int i =0; i < [evqArray count]; i++)
{
    id selector = [evqArray objectAtIndex:i];
        NSLog(@"selector: %@", selector);

    NSString *labelText = selector[@"label"];
        NSLog(@"labelText: %@", labelText);

    NSString *evqQualifierID = selector[@"event_qualifier_id"];
        NSLog(@"evqQualifierID: %@", evqQualifierID);

    NSInteger b = [evqQualifierID integerValue];

    // for every item in the array, add 35 pixels to the xPosStart
    _yPosStart = _yPosStart + 35;

    // Convert integer into CGFloat for positioning
    CGFloat yPosition = _yPosStart;

    UILabel *switchLabel = [[UILabel alloc] initWithFrame:CGRectMake(60, yPosition, 240, 27)];

    [switchLabel setText:labelText];

    _qualifierSwitch = [[UISwitch alloc] initWithFrame:CGRectMake(0, yPosition, 0, 0)];

    // add an incrementing tag so the siwtch interactions are unique
    _qualifierSwitch.tag = b;

    [myScroll addSubview:_qualifierSwitch];

    [myScroll addSubview:switchLabel];

    //Matcht the saved value to the switch
    _dbSwitchValue = [_evqSavedValues objectForKey:evqQualifierID];
        NSLog(@"myString2: %@", _dbSwitchValue);

    if ([_dbSwitchValue isEqualToString:@"Yes"]) {
        [_qualifierSwitch setOn:YES animated:YES];
    } else {
        [_qualifierSwitch setOn:NO animated:YES];
    }

    if (_qualifierSwitch.on)
    {
        _editSwitchValue = @"Yes";

    } else {
        _editSwitchValue = @"No";
    }

    [_qualifierSwitch addTarget:self action:@selector(evqChangeSwitch:) forControlEvents:UIControlEventTouchUpInside];

    [_evqValuesDict setObject:_editSwitchValue forKey:evqQualifierID];

}

- (void)evqChangeSwitch:(id)sender {
NSLog(@"evqSwitch: %@", _qualifierSwitch);
NSLog(@"_evqValuesDict at start of method: %@", _exqValuesDict);

//get the sender's tag value
NSInteger i = [sender tag];

//cast the tag value into a string for comparison to the string value for purposes of matching the dictionary key
NSString *tagID = [NSString stringWithFormat:@"%ld", (long)i];

NSLog (@"tagID:  %@:", tagID);

if([sender isOn]){

    NSLog(@"Switch is ON for tagID: %@", tagID);
    //Set string for display purposes elsewhere
    switchValue = @"Yes";
    [_exqValuesDict removeObjectForKey:tagID];
    [_evqValuesDict setObject:switchValue forKey:tagID];

} else {

    NSLog(@"Switch is OFF for tagID: %@", tagID);
    //Set string for display purposes elsewhere
    switchValue = @"No";
    [_exqValuesDict removeObjectForKey:tagID];
    [_evqValuesDict setObject:switchValue forKey:tagID];

}

NSLog(@"_evqValuesDict at end of method: %@", _evqValuesDict);

}

Here are the logs at the beginning of the evqChangeSwitch method, and at the end.

_evqValuesDict at start of method: {
3 = No;
1 = No;
2 = No;
}

evqValuesDict at end of method: {
3 = No;
2 = No;
2 = Yes;
1 = No;
}

So you can see that it appears that for each switch that has been selected, a duplicate is being created.

Once the new, apparently duplicated value is in the NSMutableDictionary, the value for that key is actually properly updated.

I am building and testing against iOS9 and running XCode 7.1

Answer 1

Solved it by simplifying everything. And I think it wasn't working because I was trying to use a new string (new memory pointer) to update objects for keys . So my guess is (without having completely researched this) is that when NSMutableDictionary is doing setValue: for Key: it is referencing the memory address of the object, NOT the string value.

The main change I made was to use a single property evqQualifierID to keep track of the dictionary keys.

h.

@property (nonatomic, strong) NSString *evqQualifierID;

m.

- (void)evqChangeSwitch:(id)sender {
NSLog(@"evqSwitch: %@", _qualifierSwitch);
NSLog(@"_evqValuesDict at start of method: %@", _exqValuesDict);

//get the sender's tag value
NSInteger i = [sender tag];

//cast the tag value into a string for comparison to the string value for purposes of matching the dictionary key
NSString *tagIDString = [NSString stringWithFormat:@"%ld", (long)i];

NSLog (@"tagIDString:  %@:", tagIDString);

if([sender isOn]){

    NSLog(@"Switch is ON for tagIDString: %@", tagIDString);
    //Set string for display purposes elsewhere
    switchValue = @"Yes";

} else {

    NSLog(@"Switch is OFF for tagIDString: %@", tagIDString);
    //Set string for display purposes elsewhere
    switchValue = @"No";
}

[_evqValuesDict setObject:switchValue forKey:_evqQualifierID];

NSLog(@"_evqValuesDict at end of method: %@", _evqValuesDict);
}