我已成功将以下方法从Obj-C转换为Swift:
在学习了在Swift中如何用闭包替代块之后。
Obj-C:
- (RACSignal *)fetchCurrentConditionsForLocation:(CLLocationCoordinate2D)coordinate {
NSString *urlString = [NSString stringWithFormat:@"http://api.openweathermap.org/data/2.5/weather?lat=%f&lon=%f&units=imperial", 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];
}];
}
Swift:
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)
return fetchJSONFromURL(url).map { json in
return MTLJSONAdapter.modelOfClass(WXCondition.self, fromJSONDictionary: json as NSDictionary, error: nil)
}
}
然而,我在将下面的返回映射块转换为Swift时遇到了困难:
func fetchHourlyForecastForLocation(coordinate: CLLocationCoordinate2D) -> RACSignal {
var urlString = NSString(format: "http://api.openweathermap.org/data/2.5/forecast?lat=%f&lon=%f&units=metric&cnt=12", coordinate.latitude, coordinate.longitude)
let url = NSURL.URLWithString(urlString)
/* Original Obj-C:
return [[self fetchJSONFromURL:url] map:^(NSDictionary *json) {
RACSequence *list = [json[@"list"] rac_sequence];
return [[list map:^(NSDictionary *item) {
return [MTLJSONAdapter modelOfClass:[WXCondition class] fromJSONDictionary:item error:nil];
}] array];
}];
}
*/
// My attempt at conversion to Swift
// (I can't resolve `rac_sequence` properly). Kind of confused
// as to how to cast it properly and return
// it as an "rac_sequence" array.
return fetchJSONFromURL(url).map { json in
let list = RACSequence()
list = [json["list"] rac_sequence]
return (list).map { item in {
return MTLJSONAdapter.modelOfClass(WXCondition.self, fromJSONDictionary: item as NSDictionary, error: nil)
} as NSArray
}
}
如果有帮助的话,这就是rac_sequence
的含义:
- (RACSequence *)rac_sequence {
return [RACArraySequence sequenceWithArray:self offset:0];
}
RACArraySequence()
:
+ (instancetype)sequenceWithArray:(NSArray *)array offset:(NSUInteger)offset;
编辑:fetch方法返回的是RACSignal而不是NSArray
:
func fetchJSONFromURL(url: NSURL) -> RACSignal {
}
NSURL(string:urlString)
代替NSURL.urlWithString
。你已经在NSString
中使用它了,但没有在NSURL
中使用 :p - Jack