> On 8 Jun 2015, at 06:14, Greg Parker <gpar...@apple.com> wrote:
>
>
>> On Jun 6, 2015, at 2:43 AM, Roland King <r...@rols.org> wrote:
>>
>>
>>
>> public class RDKBLEService : NSObject
>> {
>> let peripheral : CBPeripheral
>>
>> public init( peripheral: CBPeripheral )
>> {
>> self.peripheral = peripheral
>> }
>> }
>>
>> It’s a designated initialiser, there’s a superclass (NSObject) but the
>> initialiser doesn’t call a designated initialiser of the superclass.
>> According to the rules I was just re-re-re-reading about Swift
>> initialisation, it’s required to call a superclass designated initialiser
>> from your derived class. I was looking to see if I could find an exception
>> to the rule which this fell under but can’t.
>
> There is an exception in the designated initializer rule: if your superclass
> is NSObject then you may omit the call to -[NSObject init]. The compiler
> knows that -[NSObject init] does nothing, so it allows this as a performance
> optimization.
>
> NSObject Class Reference:
> "The init method defined in the NSObject class does no initialization; it
> simply returns self."
> There is lots of existing code that would break if we changed that, so we
> can't even if we wanted to.
>
Seems not to matter if it’s NSObject or not, appears to be subclassing any
class with one and only one no-arg initializer gets one implicitly synthesized
in for you. This is Swift we’re talking about in this case, not obj C by the
way. eg this compiles too even though Y’s init doesn’t have a super.init() call
in it per the documented Swift rules.
import Cocoa
class X
{
let i : Int
init()
{
i = 123
}
}
class Y : X
{
let j : Int
init( jj : Int )
{
j = jj
}
}
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