Firebase Data Retrieval - Edit Annotation

问题

I am currently working on an application where the users can save an annotation on their map and this all works great! The map location, name and subtitle are all sent to the database and the pin is put into the map.

However, I am struggling to figure out how to pull this data back down from [Firebase][1] so the users are able to edit the previous information and then update it.

回答1:

To read data, you want to use the observe attribute from your firebase reference. This returns a snapshot consisting of your data.

Since your Skatepark class already has a snapshot constructor, all you'd have to do is pass the snapshot to it and create your object.

reference.child("yourNode").observeSingleEvent(of: .value, with: { (snapshot) in

/* Two things can happen here. Snapshot can either consist of one element or multiple.
   To handle this, you want to iterate through the snapshot, create your Skatepark
   object and populate it into your global skatepark array.
*/

    if snapshot.value is NSNull
    {
        print("Error Getting Snapshot")
    }
    else
    {
        for (child in snapshot.children)
        {
            let snap = child as! FIRDataSnapshot
            let skateObject = Skatepark(child) // this calls the constructor which take snapshot as parameter
            globalSkateParkArray.append(skateObject)
        }
    }

})

To update your values, this is all you need.

Personal Recommendations

1. Consider making coordinate, name, subtitle into var instead of let.

2. Consider creating a Skatepark object first out of the data before sending it to the database. This constructor should do the trick

   init(coordinate: CLLocationCoordinate2D, name: String, subtitle: String, type: SkateboardType, editable: Bool)
   {
       self.coordinate = coordinate
       self.name = name
       self.subtitle = subtitle
       self.type = type
       self.editable = editable
   }
   

3. I'd create a dictionary variable inside Skatepark that creates a dictionary from the object. This way I won't have ["lat": locationManager.location?.coordinate.latitude, "lng": locationManager.location?.coordinate.longitude, "name": skateTitleText, "subtitle": skateStyleText, "type": (selected - 1), "editable": true] floating all around my codebase.

So have this in your class

var dictionary: [String:Any]
{
    return
    [
        "lat": coordinate.latitude,
        "lng": coordinate.longitude,
        "name": title,
        "subtitle": subtitle,
        "type": type,
        "editable": editable
    ]
}

Every time you'd want a dictionary out of your object, simply use object.dictionary

来源：https://stackoverflow.com/questions/44028023/firebase-data-retrieval-edit-annotation