如何使用Firestore Geopoint for Social Media app获取基于位置的帖子(swift Xcode)

let db = Firestore.firestore()
let postsCollection = db.collection("posts")

let latitude: Double = 37.7749
let longitude: Double = -122.4194
let location = GeoPoint(latitude: latitude, longitude: longitude)

let postDocument = postsCollection.document()
postDocument.setData([
    "content": "这是一个基于位置的帖子",
    "location": location
])

let center = GeoPoint(latitude: centerLatitude, longitude: centerLongitude)
let radiusInKm: Double = 10

let query = postsCollection.whereField("location", isNearTo: center, within: radiusInKm)
query.getDocuments { (snapshot, error) in
    if let error = error {
        print("获取帖子失败：\(error.localizedDescription)")
    } else {
        for document in snapshot!.documents {
            let data = document.data()
            let content = data["content"] as? String
            let location = data["location"] as? GeoPoint
            
            // 处理帖子数据
        }
    }
}