How to modify string element of a NSArray using fast enumeration? [duplicate]

Question

This question already has answers here:

Avoiding "NSArray was mutated while being enumerated" (11 answers)

Closed 9 years ago.

Can anyone pls suggest how to string element of an NSArray using fast enumeration. Its very easy to do the same with normal for loop. Below code works fine

_tempArray = [[NSMutableArray alloc] initWithObjects:@"A",@"B",@"C",@"D",@"E",@"F", nil];

NSUInteger i=0;
for (; i<[_tempArray count]; i++) {
     if ([[_tempArray objectAtIndex:i] isEqualToString:@"A"]) {
            [_tempArray replaceObjectAtIndex:i withObject:@"a"];
      }
}

I want to do the same as above code does with fast enumeration. I tried the below code but it gives *****Error: Collection <__NSArrayM: 0x610000043090> was mutated while being enumerated.******, which means it is not possible to modify the collection while enumerating it. Can anyone suggest any way to achieve it.**

NSUInteger j=0;
    for (NSString *temp in _tempArray) {
        if ([temp isEqualToString:@"A"]) {
            [_tempArray replaceObjectAtIndex:j withObject:@"a"];
        }
        j++;
    }

Answer 1

How to modify string element of a NSArray using fast enumeration?

Don't. You are not supposed to modify the array during enumeration. It's not an arbitrary restriction -- doing so may result in logical errors.

If you want to modify/transform an array, then use an explicitly indexed for loop instead.

Answer 2

You can tighten up the code with the array indexing syntax:

for (int i=0; i<_tempArray.count; i++) {
    if ([_tempArray[i] isEqualToString:@"A"]) {
        _tempArray[i] = @"a";
    }
}