Swift enum and CBCharacteristicProperties

Question

While using the CoreBluetooth framework to setup the device as a peripheral manager, I'm running into difficulties with how Swift handles enumerations.

Specifically, the initializer for CBMutableCharacteristic takes an enum for the properties argument:

init!(type UUID: CBUUID!, properties: CBCharacteristicProperties, value: NSData!, permissions: CBAttributePermissions)

CBCharacteristicProperties is an Int -backed enumeration. If using ObjectiveC, the initializer would accept multiple values for properties by using the bitwise OR | operator. In Swift, the enum does not directly allow use of bitwise OR, but one can perform it on the rawValues that back the cases:

let properties = CBCharacteristicProperties.Read.rawValue | CBCharacteristicProperties.Notify.rawValue

Now, properties is of type Int , which means it can not be passed to the above initializer. ( 'Int' is not convertible to 'CBCharactersiticProperties' ) Therefore, I attempted to create an instance of the enumeration from the "raw" value:

let cbProperties = CBCharacteristicProperties(rawValue: properties)

However, at runtime this resolves to nil . The Int that results from the bitwise OR does not match any of the enum cases. Passing nil for the properties parameter to the initializer results in a runtime error.

Is it possible to accomplish this in Swift?

Answer 1

Objective-C:

[[CBMutableCharacteristic alloc] initWithType:[CBUUID UUIDWithString:CHARACTERISTIC_UUID]
                                   properties:CBCharacteristicPropertyNotify |
                                   CBCharacteristicPropertyRead
                                   value:nil
                                   permissions:CBAttributePermissionsReadable]

Swift:

CBMutableCharacteristic(type: CBUUID(string:CHARACTERISTIC_UUID),
                                properties: [CBCharacteristicProperties.Read,CBCharacteristicProperties.Notify],
                                value: nil,
                                permissions: CBAttributePermissions.Readable)

Answer 2

The syntax is Swift is exactly the same as in Objective C - Use the | character to separate the values -

var someCharacteristic=CBMutableCharacteristic(type: CBUUID(string:"someUUID"), 
  properties:CBCharacteristicProperties.Read|CBCharacteristicProperties.Write ,
  value: nil, 
  permissions: CBAttributePermissions.Readable|CBAttributePermissions.Writeable)

Update While this syntax works on iOS with Xcode 6.2 it doesn't work for an OS X target - looks like a bug