I’m getting a couple of odd new compile errors with Xcode 7. These are in
classes that subclass NSObject and add an initializer that’s declared as a
designated initializer, but do not implement -init because it’s not valid to
initialize them without parameters. The new error says “Method override for the
designated initializer of the superclass ‘-init’ not found”.
@interface Flump : NSObject
- (instancetype) initWithString: (NSString*)str NS_DESIGNATED_INITIALIZER;
@end
@implementation Flump // <- error reported on this line
- (instancetype)initWithString: (NSString*)str {
self = [super init];
if (self) {
//...
}
return self;
}
@end
I suppose the error points out that someone initializing a Flump with -init
would call the inherited -init from NSObject without any Flump-specific
initialization occurring. Which seems sort of valid. So to fix the error I
added an override of -init:
- (instancetype) init {
@throw [NSException exceptionWithName: NSInternalInconsistencyException
reason: @"Flump cannot be initialized with
-init"
userInfo: nil];
}
But this didn’t fix it. The new -init method gets an error “Convenience
initializer missing a ‘self’ call to another initializer”. The only way to get
rid of this error is to add a call to -initWithString … but there’s no valid
parameter I can pass because the caller didn’t provide a string. Nor can I put
this -init call after the throw, because then the compiler complains that it’s
unreachable.
It seems as though whoever designed this hadn’t thought through the case where
a subclass wants to _get rid of_ a superclass’s designated initializer, i.e.
make it illegal to call it.
—Jens _______________________________________________
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