Question: I understand from my recent use of PHP-PDO over the last few months that you can do a PREPARE statement and then run the query. In fact I can see the usefulness of this if I'm going to either SELECT on a complex join, varying the where conditions, a repeated number of times.

Or, similarly, if I was wanting to insert multiple records.

However, if I know I only want to run a statement once, shouldn't I just EXECUTE the query? I'm basically querying the database twice.

Answer: 
You can use any Objective-C class in Swift:

```
var set = NSMutableSet()
set.addObject(foo)

```
Special case for classes derived from NSObject

given that default Equitable (& Hashable) conformance in NSObject is basically trash you'd better make sure you provide a proper 

```
static func == (lhs: YourClassDerivedFromNSObject, rhs: YourClassDerivedFromNSObject) -> Bool {

```

implementation lest you want plucking the duplicates inserted into
Set