func withExtendedLifetime<T, Result>(_: T, _: () throws -> Result) Evaluates a closure while ensuring that the given instance is not destroyed before the closure returns. Parameters: x: An instance to preserve until the execution of body is completed. body: A closure to execute that depends on the lifetime of x being extended. If body has a return value, that value is also used as the return value for the withExtendedLifetime(_:_:) method. Returns: The return value, if any, of the body closure parameter. Declaration func withExtendedLifetime<T, Result>(_ x: T, _ body: () throws -> Result) rethrows -> Result func withExtendedLifetime<T, Result>(_: T, _: (T) throws -> Result) Evaluates a closure while ensuring that the given instance is not destroyed before the closure returns. Parameters: x: An instance to preserve until the execution of body is completed. body: A closure to execute that depends on the lifetime of x being extended. If body has a return value, that value is also used as the return value for the withExtendedLifetime(_:_:) method. Returns: The return value, if any, of the body closure parameter. Declaration func withExtendedLifetime<T, Result>(_ x: T, _ body: (T) throws -> Result) rethrows -> Result