How do I put objects in an NSArray into an NSSet?

Question

I have some `NSDictionary` objects stored in an `NSArray` called `telephoneArray`. I fetch the values for the key `number` and then replace the `NSDictionary` I've just read with a new object at the same index in the array. I then want to put these new objects into an `NSSet`. How can this be achieved? See my unsuccessful attempt below. ``` // Add all telephones to this branch for (int i=0; i<[telephoneArray count]; i++) { [newTelephone setBranch:newBranch]; [newTelephone setNumber:[[telephoneArray objectAtIndex:i] valueForKey:@"number"]]; NSLog(@"%@",[[telephoneArray objectAtIndex:i] valueForKey:@"number"]); [telephoneArray replaceObjectAtIndex:i withObject:newTelephone]; NSLog(@"phone number %i = %@",i,[[telephoneArray objectAtIndex:i] valueForKey:@"number"]); } NSSet *telephoneSet = [NSSet setWithArray:telephoneArray]; NSLog(@"telephoneArray=%i",[telephoneArray count]); NSLog(@"telephoneSet=%i",[[telephoneSet allObjects] count]); ``` OUTPUT: ``` 2010-03-06 03:06:02.824 AIB[5160:650…

Accepted Answer

This is not correct:

```
NSSet *telephoneSet = [[NSSet alloc] init];
[telephoneSet setByAddingObjectsFromArray:telephoneArray];
```

That method returns an NSSet which you are doing nothing with (it doesn't add the objects to telephoneSet, it creates a new NSSet). Do this instead:

```
NSSet *telephoneSet = [NSSet setWithArray:telephoneArray]
```

Also, note that a set cannot contain duplicates unlike an array. So if you have duplicate objects in your array and you put them in a set, the duplicates will be removed which can affect the object count.

How do I put objects in an NSArray into an NSSet?

Solution

Problem