How to check the duplicate NSObjects in NSMutableArray - ios

Question

I receive data for an object person in sets of 5. Let's say name,age,gender,email,number. I did following to add the strings to NSobject:
DataObject *data=[DataObject new];
data.name=#"name";
data.age=#"age";
data.email=#"email";
//here i want to check for duplicates
[personArray addObject:data];
However, I want to check if the personArray is having the duplicate NSObjects or not.
I tried this,but it didnt work:
if(![personArray containsObject:data]){
//add data
}
Edit: Actually, this is what I am trying to do:
I am getting the JSON repsonse and I am adding the properties into array. Before I used to get only one property,in that case, I did the following to eliminate the duplicates:
[JSON[#"person"] enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
if (![obj[#"email"] isEqual:[NSNull null]] && ![personArray containsObject:obj[#"email"]] ) {
[personArray addObject:obj[#"email"]];
}
}];
Later I got 5 properties for person, so I thought instead of adding them all to the array, I used NSObject class to tie the properties together and add one person to the array.
[JSON[#"person"] enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
if (![obj[#"email"] isEqual:[NSNull null]] && ![personArray containsObject:obj[#"email"]] ) { //how to check for the duplicates here?
DataObject *data=[DataObject new];
data.name=#"name";
data.age=#"age";
data.email=#"email";
[personArray addObject:data];
}
}];

Answer 1

If you do this:
DataObject *data = [DataObject new];
You have just created a new instance of data. No other object inside the personArray can be equal to that new instance.
I assume you're actually trying to check to see if there is a data object that contains the same properties as other data objects in the personArray. There's a number of ways you could do this (I like Zaph's answer, it's clean), but for simplicity...
DataObject *data=[DataObject new];
data.name=#"name";
data.age=#"age";
data.email=#"email";
BOOL contains = NO;
for (DataObject *object in personArray) {
if ([object.name isEqualToString:data.name] && [object.age isEqualToString:data.age] && [object.email isEqualToString:data.email]) {
contains = YES;
break;
}
}
if (!contains) {
[personArray addObject:data];
}

Answer 2

You need to implements isEqual for the DataObject class. Then [personArray containsObject:data] should work.
For details see:
Equality by Mattt Thompson.
Implementing Equality and Hashing by Mike Ash