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Stephen Hancocks
Stephen Hancocks
9,271 Points

Is addObject overwriting the rest of my array?

I have a number of arrays and I want to combine them. There may be an easier way to what i have done but please bear with me. I'd like to know what's going on here.

When I run the code below all of the NSLog's within the while block appear correct - i counts up sequential, the properties change as expected, the array increases in size etc.

However, when I run the final NSLog to print the Array it shows all properties for each of the 20 objects as the same. They are all the same as the last object added. Is there something fundamental I am missing?


  NSMutableArray *combinedArray = [[NSMutableArray alloc]initWithCapacity:0];

  CombinedArrayClass *objectForCombinedArray = [[CombinedArrayClass alloc]init];

  int i = 0;
  while (i < [_array1 count]){

    [combinedCaseCredits addObject:objectForCombinedArray];
    objectForCombinedArray.month = [[_array1 objectAtIndex:i] valueForKey:@"month"];
    NSLog(@"month = %@", [[_array1 objectAtIndex:i]valueForKey:@"month"]);
    objectForCombinedArray.property1 = [[_array1 objectAtIndex:i] valueForKey:@"dataType1"];
    objectForCombinedArray.property2 = [[_array2 objectAtIndex:i] valueForKey:@"dataType2"];
    objectForCombinedArray.property3 = [[_array3 objectAtIndex:i] valueForKey:@"dataType3"];
    NSLog(@"i = %i", i);
    NSLog(@"array length = %lu", (unsigned long)[combinedCaseCredits count]);

  _combinedArray = combinedArray;

  for (CombinedArrayClass *month in combinedCaseCredits){
    NSLog(@"Month %@, Data1 %@, Data2 %@, Data3 %@", month.month, month.property1, month.property2, month.property3);

1 Answer

Stephen Hancocks
Stephen Hancocks
9,271 Points

I've resolved the issue myself.

I moved the line

CombinedArrayClass *objectForCombinedArray = [[CombinedArrayClass alloc]init];

within the loop.

I must have been copying and overwriting the only initialised objectForCombinedArray. Allocating and initialising a new objectForCombinedArray each time has built the array as I wanted.

A beginners mistake, but pleased I've found the answer myself