Attempts to start the query.
- iOS 5.0+
- macOS 10.4+
- tvOS 9.0+
- watchOS 2.0+
true when successful; otherwise,
A query may fail to start if it does not specify a
predicate, or if the query has already been started.
A query can’t be started if the receiver is already running a query or no predicate has been specified.
This method must be called from the receiver’s
operation or on the main thread. For example: