Question

I encountered a very strange behavior when i m trying to insert a NSMutableDictonary into an NSMutableArrey while the app is in a for-loop.

The NSMutableDict is constructed every for-step and added to an array. but it doesnt work… when i print out the array after the for loop, every NSMutableDictonary in the array is the same – After some logging, i saw that every for-step, all dictionarys in the array gets replaced and one is added at the end… thats a strange behavior and i dont know whats causing this…
If i add the currentID (see code) to the array insted of the dictonary, in the end, all looks fine…
whats the problem here?

NSArray *relativeIAbnormality = [[NSArray alloc] init];
NSMutableDictionary *tempDict = [[NSMutableDictionary alloc] init];
NSMutableArray *tempArray = [[NSMutableArray alloc] init];

for (int q = 0; q < [measureData.list count]; q++) {
    [tempDict removeAllObjects];
    NSString *currentId = [[measureData.list objectAtIndex:q] valueForKey:@"id"];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"id == %@", currentId];
    NSInteger count = [[lastMeasureData.list filteredArrayUsingPredicate:predicate] count];

    if(count > 0){

        // get the answer Value for the CURRENT measure
        float theValue = 0;
        theValue = [[[[measureData.list objectAtIndex:q] objectForKey:@"propertys"] valueForKey:@"answerValue"] floatValue];

        theValue = theValue/100;

        if(theValue > 10){
            theValue = 10;
        }else if (theValue < 0) {
            theValue = 0;
        }

        // get the answer Value for the LAST measure
        float theNewValue = 0;

        theNewValue = [[[[[lastMeasureData.list filteredArrayUsingPredicate:predicate] objectAtIndex:0] objectForKey:@"propertys"] valueForKey:@"answerValue"] floatValue];

        theNewValue = theNewValue/100;

        if(theNewValue > 10){
            theNewValue = 10;
        }else if (theNewValue < 0) {
            theNewValue = 0;
        }

        // gets the reltaive
        theValue = theValue - theNewValue;
        NSNumber *dif = [NSNumber numberWithFloat:theValue];

        [tempDict setObject:currentId forKey:@"id"];
        [tempDict setObject:dif forKey:@"dif"];

        //NSLog(@"tempDict: %@", tempDict);

        [tempArray addObject:tempDict];
        //NSLog(@"tempArray: %@", tempArray);
    }
}
//NSLog(@"full tempArray: %@", tempArray);

Answer 1

You keep using the very same instance of tempDict. Move that alloc-init pair of your temp-dict inside the loop.

NSArray *relativeIAbnormality = [[NSArray alloc] init];
NSMutableArray *tempArray = [[NSMutableArray alloc] init];
for (int q = 0; q < [measureData.list count]; q++) 
{
    NSMutableDictionary *tempDict = [[NSMutableDictionary alloc] init];
    ...
}