Swiftで日付の比較 SwiftDateの利用 Firebase 忘備録

private func checkPoints(callback: @escaping ((Int?, String?)->Void)) {

 
//userREFはviewwillAppearでFirebase Authから documentをget下記参照 
        userREF.collection(DIARY_REF).order(by: CREATED_AT, descending: true).limit(toLast: 2).getDocuments { (snap, error) in
 
            if let error = error?.localizedDescription {
                callback(0, error)
                return
            }

            guard let dateStr = snap?.documents.compactMap({ $0[CREATED_AT] as? Timestamp }), dateStr.count == 2 else {
                callback(0,nil)
                return
            }

//dateValueでNSDate型へキャスト
            let days = dateStr.compactMap({$0.dateValue()})
            let firstDay = days[0]
            let secondDay = days[1]


//2つ目のdateに 1日プラスする処理も簡単            
            if (secondDay + 1.days).compare(toDate: firstDay, granularity: .day) == ComparisonResult.orderedSame {
                callback(10, nil)
                
            }else{
                callback(0,nil)
            }

        }

    }

//trailing clousureを利用

      checkPoints { (point, err) in
            if let err = err { print(err) }

//ここへcallbackが返却される
            guard let point = point else { return }
            User.loggedIn?.points += point
            User.loggedIn?.save()
            
            self.uploadPhoto() { imgRef in self.saveDiary(photoRef: imgRef) }
        }

//メンバ変数
    let db = Firestore.firestore()
    private var userId:String?
    var userREF: DocumentReference!


override func viewWillAppear(_ animated: Bool) {
        userId =  Auth.auth().currentUser!.uid
        userREF =  db.collection(USER_REF).document(userId!)
}