如何检查数组中的NSMutableArray是否已经有(__bridge id)对象?

I am trying to add ABRecordRef item into my NSMutableArray. Just learned that It's needed to cast the C TypeDef into Objective-C id type using (_bridge id). So, before adding new items into the array, I want to check if the object is already in the array. Therefore, i tried using [nsmutablearray containsObject] but it does not seem to be working. Duplicate items still get added into the array. Do you know what could be wrong here?I am trying to add ABRecordRef item into my NSM