Question

When I remove array, do I have remove each element of dictionary also?

NSMutableArray *myArry = [NSMutableArray arrayWithCapacity:100];
NSMutableDictionary *myDic = [NSMutableDictionary dictionaryWithCapacity:10];
[myArray addObject:myDic]; // this is done in loop


[myDic removeAllObjects]; // Is this necessary?
[myArray removeAllObjects];

Answer 1

No. When you release an array, every item inside is automatically send a release message so you are not required to remove them, release them or adjust them other that simply releasing the array using -[NSArray release]

The correct code is

NSMutableArray *myArry = [[NSMutableArray alloc] initWithCapacity:100];
NSMutableDictionary *myDic = [NSMutableDictionary dictionaryWithCapacity:10];
[myArray addObject:myDic]; // this is done in loop
…
[myArray release]; // To dispose of the array and it's contents. No need to remove objects

A NSDictionary behaves in the same way, that is, you do not need to remove them, only release them. In the move example, the dictionaries you are adding are autoreleased meaning that once myArray releases them, they will be dealloc’d