CODEWITHSUNDEEP
objective-cswift
btype
btype

Reputation: 1576

Cannot convert the expression's type 'Void' to type 'String!'

I tried to call a objective-c method out of swift and am getting this weird error:

Cannot convert the expression's type 'Void' to type 'String!'

Swift code:

XNGAPIClient.sharedClient().putUpdateGeoLocationForUserID("me",
        accuracy: 3000,
        latitude: location.coordinate.latitude as CGFloat,
        longitude: location.coordinate.longitude as CGFloat,
        ttl: 420, success: { (JSON: AnyObject!) in },
        failure: { (error: NSError!) in })

Objective-C method:

- (void)putUpdateGeoLocationForUserID:(NSString*)userID
                             accuracy:(CGFloat)accuracy
                              latitude:(CGFloat)latitude
                             longitude:(CGFloat)longitude
                                   ttl:(NSUInteger)ttl
                               success:(void (^)(id JSON))success
                               failure:(void (^)(NSError *error))failure

If I convert everything to the suggested types:

XNGAPIClient.sharedClient().putUpdateGeoLocationForUserID("me" as String,
        accuracy: 3000 as CGFloat,
        latitude: location.coordinate.latitude as CGFloat,
        longitude: location.coordinate.longitude as CGFloat,
        ttl: 420 as Int,
        success: { (JSON: AnyObject!) in },
        failure: { (error: NSError!) in })

I get the following error: Cannot convert the expression's type 'Void' to type 'StringLiteralConvertible'

Upvotes: 4

Views: 2676

Answers (1)

Matt Gibson
Matt Gibson

Reputation: 38238

Your problem is the location.coordinate.latitude and location.coordinate.longitude parameters. I can reproduce your problem if I make those parameters Int, for example. So, try:

XNGAPIClient.sharedClient().putUpdateGeoLocationForUserID("me" as String,
    accuracy: 3000 as CGFloat,
    latitude: CGFloat(location.coordinate.latitude),
    longitude: CGFloat(location.coordinate.longitude),
    ttl: 420 as Int,
    success: { (JSON: AnyObject!) in },
    failure: { (error: NSError!) in })

...that is, using the CGFloat constructor rather than the down casting as for those parameters. (I'd take a guess that there's something clever going on behind the scenes for the 3000 literal that looks like it should be an Int, otherwise that one probably wouldn't work, either...)

I'd also raise a bug with Apple for the very unhelpful error message. I've seen a few of those from calls to Objective C with the wrong parameter types.

Upvotes: 2

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