CODEWITHSUNDEEP
iosobjective-cxcodeuitableviewnsmutablearray
Jason Silberman
Jason Silberman

Reputation: 2491

Deleting objects within a for loop from a NSMutableArray

I am working with a UITableView and for each of the objects in the array that is the datasource for the UITableView, I am deleting them if they meet a certain if statement. My problem is that it only deletes every-other object from the array.

Code:

UIImage *isCkDone = [UIImage imageNamed:@"UITableViewCellCheckmarkDone"];
int c = (tasks.count);
for (int i=0;i<c;++i) {
    NSIndexPath *tmpPath = [NSIndexPath indexPathForItem:i inSection:0];
    UITableViewCell * cell = [taskManager cellForRowAtIndexPath:tmpPath];
    if (cell.imageView.image == isCkDone) {
        [tasks removeObjectAtIndex:i];
        [taskManager deleteRowsAtIndexPaths:@[tmpPath]
                withRowAnimation:UITableViewRowAnimationLeft];
    }
}

What is wrong with this?

Upvotes: 1

Views: 724

Answers (2)

John Sauer
John Sauer

Reputation: 4421

If you wanted to keep your loop running forwards, you could either:

decrement i when your condition is met and you removeObjectAtIndex

    if (cell.imageView.image == isCkDone) {
        ...
        --i ;
        ...
    }

or increment i only when your condition is not met:

for ( int i=0 ; i<c ; ) {
    ...
    if (cell.imageView.image == isCkDone) {
        ...
    } else {
    ++i ;
    }

Upvotes: 1

herzbube
herzbube

Reputation: 13378

You must run your loop backwards, i.e. 

for (int i=c-1;i>=0;--i)

If you are running it the other way round, removing an object at index position i moves the objects in the array that are behind i one position forward. In the end you will even run over the bounds of your array.

Upvotes: 6

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