Question

Currently, I have edited a delegate function that adds Exercise objects to an NSMutableArray. However, I would not like to add duplicate objects, instead, if the object is already in the array, i’d like to simply access that particular object.

Here is my code:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

    UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
    NSString *str = cell.textLabel.text; // Retrieves the string of the selected cell.

    Exercise *exerciseView = [[Exercise alloc] initWithExerciseName:str];
    WorkoutManager *workoutManager = [WorkoutManager sharedInstance];

    if (![[workoutManager exercises] containsObject:exerciseView]) {
        [[workoutManager exercises] insertObject:exerciseView atIndex:0];
        [self presentModalViewController:exerciseView animated:YES];
        NSLog(@"%@", [workoutManager exercises]); 
    }
    else {
        [self presentModalViewController:exerciseView animated:YES];
        NSLog(@"%@", [workoutManager exercises]); 
    }
}

I thought this would work, however, when I ran my code and NSLogged my array, it showed that when I clicked on the same cell, two seperate objects were created. Any help?

Answer 1

I would say this is your culprit:

Exercise *exerciseView = [[Exercise alloc] initWithExerciseName:str];

You’re creating a new object each time so technically, it’s not in the array. The containsObject method is just iterating through the array and calling isEqual on each object. I haven’t tested this but theoretically, in your custom Exercise object, you could override the isEqual method to compare the exercise name properties and return true if they match. See, EVERYTHING has to match up when you are using containsObject so even if all the properties are the same, the objectid is not.

Easy fix without having to see your Exercise implementation:

Exercise *exerciseView = nil;

For(Exercise *exercise in [[WorkoutManager sharedInstance] exercises]){
    if(exercise.exerciseName == str) {
        exerciseView = exercise;
        break;
    }
}

if(exerciseView == nil) {
    exerciseView = [[Exercise alloc] initWithExerciseName:str];
    [[workoutManager exercises] insertObject:exerciseView atIndex:0];
}

[self presentModalViewController:exerciseView animated:YES];

Hope this helps explain WHY its happening. I didn’t test this code since there are some missing pieces but you should get the idea. Have fun!