swift - 过滤Firebase数据[iOS]

Question

我的Firebase具有这种配置。 https://screenshots.firefox.com/s0UNlw3IOKEeFCCr/console.firebase.google.com

从iOS，我试图获取所有经度和纬度在一定范围内的数据。是否可以从firebase进行过滤，或者我必须下载所有数据，然后在iOS中进行过滤。

func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool) {
    let rect = mapView.visibleMapRect
    let neMapPoint = MKMapPointMake(MKMapRectGetMaxX(rect), rect.origin.y)
    let swMapPoint = MKMapPointMake(rect.origin.x, MKMapRectGetMaxY(rect))
    let neCoord = MKCoordinateForMapPoint(neMapPoint)
    let swCoord = MKCoordinateForMapPoint(swMapPoint)

    getData(neCoord, swCoord)
}

private func getData(_ ne: CLLocationCoordinate2D, _ sw: CLLocationCoordinate2D) {
    let ref = Database.database().reference().child("posts")

}

我想获取所有帖子项，这些项的纬度小于ne纬度，比sw纬度小得多，经度相同。谢谢。

Answer 1

您将创建一个Post对象。就像是：

struct Post {
    let latitude: String
    let longitude: String
    init(dictionary: [String: Any]) {
        self.latitude = dictionary["latitude"] as? String ?? ""
        self.longitude = dictionary["longitude"] as? String ?? ""
    }
}

然后在文件中创建一个帖子数组：

var posts: [Post]()
private func getData(_ ne: CLLocationCoordinate2D, _ sw: 
     CLLocationCoordinate2D) {
     let ref = Database.database().reference().child("posts")
     ref.observeSingleEvent(of: .value, with: { (snapshot) in
     guard let dictionaries = snapshot.value as? [String: Any] else {return}
     dictionaries.forEach(key, value) {
     guard let dictionary = value as? [String: Any] else {return}
     guard let latitude = dictionary["latitude"] else {return}
     guard let longitude = dictionary["longitude"] else {return}

//check if latitude is less than ne latitude and gretaer than sw lattitude and the same for longitude, then append to array. 

    let post = Post(dictionary: dictionary)
    posts.append(post)

    } 
        })
                }) { (err) in
        print(err)
    }
}

然后，您将得到一个数组，其中包含具有正确的经度和纬度的帖子。这是一个粗略的想法。