Return RACSignal method in Swift

Question

I have the following method in Obj-C:

- (RACSignal *)fetchCurrentConditionsForLocation:(CLLocationCoordinate2D)coordinate {
    NSString *urlString = [NSString stringWithFormat:@"http://api.openweathermap.org/data/2.5/weather?lat=%f&lon=%f&units=metric", coordinate.latitude, coordinate.longitude];
    NSURL *url = [NSURL URLWithString:urlString];

    return [[self fetchJSONFromURL:url] map:^(NSDictionary *json) {
        return [MTLJSONAdapter modelOfClass:[WXCondition class] fromJSONDictionary:json error:nil];
    }];
}

My conversion to Swift:

func fetchJSONFromURL(url: NSURL) -> RACSignal {

}

func fetchCurrentConditionsForLocation(coordinate: CLLocationCoordinate2D) -> RACSignal {
    let urlString = NSString(format: "http://api.openweathermap.org/data/2.5/weather?lat=%f&lon=%f&units=metric", coordinate.latitude, coordinate.longitude)
    let url = NSURL.URLWithString(urlString)

    // Convert to Swift?        
    return [[self fetchJSONFromURL:url] map:^(NSDictionary *json) {
        return [MTLJSONAdapter modelOfClass:[WXCondition class] fromJSONDictionary:json error:nil];
    }];
}

Having trouble with this map in Swift:

return [[self fetchJSONFromURL:url] map:^(NSDictionary *json) {
    return [MTLJSONAdapter modelOfClass:[WXCondition class] fromJSONDictionary:json error:nil];
}];

Everything is compiling properly, but is there a better way of doing this?

Answer 1

I haven't tried in a project, but perhaps this wil do

return fetchJSONFromURL(url).map { (json: NSDictionary) in
    return MTLJSONAdapter.modelOfClass(WXCondition.self, fromJSONDictionary: json, error: nil)
} as RACSignal