使用 Google Maps API 在 Swift 3 中查找 2 个位置之间的驾驶/步行距离

Question

我正在尝试使用 Google Maps API 获取两个位置之间的行车/步行距离。我正在将我的应用程序从 Objective-c 更新到 Swift 3，现在我一直坚持将这段代码转换为 Swift 3。

NSString *dist;
NSString *strUrl = [NSString stringWithFormat:@"http://maps.googleapis.com/maps/api/directions/json?origin=%f,%f&destination=%f,%f&sensor=false&mode=%@", closestLocation.coordinate.latitude,  closestLocation.coordinate.longitude, _currentUserLocation.coordinate.latitude,  _currentUserLocation.coordinate.longitude, @"DRIVING"];
NSURL *url = [NSURL URLWithString:[strUrl stringByAddingPercentEncodingWithAllowedCharacters:NSCharacterSet.URLQueryAllowedCharacterSet]];
NSData *jsonData = [NSData dataWithContentsOfURL:url];
if(jsonData != nil)
{
    NSError *error = nil;
    id result = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&error];
    NSMutableArray *arrDistance=[result objectForKey:@"routes"];
    if ([arrDistance count]==0) {
        NSLog(@"N.A.");
    }
    else{
        NSMutableArray *arrLeg=[[arrDistance objectAtIndex:0]objectForKey:@"legs"];
        NSMutableDictionary *dictleg=[arrLeg objectAtIndex:0];

        dist = [NSString stringWithFormat:@"%@",[[dictleg   objectForKey:@"distance"] objectForKey:@"text"]];
    }
}
else{
    NSLog(@"N.A.");
}

我尝试使用 Swiftify 之类的工具，但处处出错。我现在拥有的是：

var dist: String = ""
var strUrl: String = "http://maps.googleapis.com/maps/api/directions/json?origin=\(closestLocation!.coordinate.latitude),\(closestLocation!.coordinate.longitude)&destination=\(currentUserLocation!.coordinate.latitude),\(currentUserLocation!.coordinate.longitude)&sensor=false&mode=\("DRIVING")"
var url = URL(string: strUrl)
var jsonData = Data(contentsOf: url!)
    if (jsonData != nil) {
        var error: Error? = nil
        var result: Any? = try? JSONSerialization.jsonObject(with: jsonData, options: JSONSerialization.ReadingOptions.Element.mutableContainers)
        var arrDistance: [Any]? = (result?["routes"] as? [Any])
        if arrDistance?.count == 0 {
            print("N.A.")
        }
        else {
            var arrLeg: [Any]? = ((arrDistance?[0] as? [Any])?["legs"] as? [Any])
            var dictleg: [AnyHashable: Any]? = (arrLeg?[0] as? [AnyHashable: Any])

            dist = "\(dictleg?["distance"]["text"])"
        }
    }
    else {
        print("N.A.")
    }

我现在的错误如下：

使用 Data(contentsOf: url!) 它告诉我“调用可以抛出，但它没有标有 'try' 并且错误未处理

而且它不喜欢我如何将 [Any] 用于我的 arrDistance 变量。

如果有人知道如何在 Swift 3 中实现这个 API 调用，那将非常有帮助。谢谢

Answer 1

什么编译器说Data(contentsOf:) 会出现throws 异常，所以你需要用do catch 块来处理它。现在正如评论中所建议的，您需要使用dataTask(with:) 而不是Data(contentsOf:) 来下载数据。您也可以使用您的代码制作完成块，因此请在您的代码中进行如下更改。

func getDistance(completion: @escaping(String) -> Void) {

    var dist = ""
    let strUrl = "http://maps.googleapis.com/maps/api/directions/json?origin=\(closestLocation!.coordinate.latitude),\(closestLocation!.coordinate.longitude)&destination=\(currentUserLocation!.coordinate.latitude),\(currentUserLocation!.coordinate.longitude)&sensor=false&mode=\("DRIVING")"
    let url = URL(string: strUrl)!
    let task = URLSession.shared.dataTask(with: url, completionHandler: { (data, response, error) in
        guard let data = data, error == nil else {
            print(error?.localizedDescription ?? "")
            completion(dist)
            return
        }
        if let result = (try? JSONSerialization.jsonObject(with: data, options: [])) as? [String:Any],
            let routes = result["routes"] as? [[String:Any]], let route = routes.first,
            let legs = route["legs"] as? [[String:Any]], let leg = legs.first,
            let distance = leg["distance"] as? [String:Any], let distanceText = distance["text"] as? String {

            dist = distanceText
        }
        completion(dist)
    })
    task.resume()
}

现在只需像这样调用getDistance函数。

self.getDistance { (distance) in
    //Update UI on main thread
    DispatchQueue.main.async {
        print(distance)
        self.label.text = distance
    }
}