ios - 为什么我的从数据库中提取信息的函数不起作用?
问题描述
我正在尝试从我的 Firebase 数据库中提取数据列表。下面是我的代码。viewDidLoad();
然而,这两个函数都在我的数据库中被调用,print(theLikeArray)
即使我的数据库已完全填充,它们也会返回空括号。
下面是我目前正在使用的代码。第一个函数用于从数据库中检索所有信息,而第二个函数用于填充数据库。第二个函数在第一个函数之前调用。
func retriveDiscounts() {
let likesDB = Database.database().reference().child("Discounts")
likesDB.observe(.childAdded) { (snapshot) in
let snapshotValue = snapshot.value as! Dictionary<String , String>
let businessID = Int(snapshotValue["BusinessID"]!)
let businessName = snapshotValue["businessName"]!
let DateNumber = Int(snapshotValue["DateNumber"]!)
let theDeal = snapshotValue["theDeal"]!
let phoneNumber = snapshotValue["PhoneNumberText"]!
let imageName = snapshotValue["ImageName"]!
let dateText = snapshotValue["DateText"]!
let phoneNumberInteger = Int(snapshotValue["phoneNumberInteger"]!)
let companyLogo = snapshotValue["companyLogo"]!
let r1 = Int(snapshotValue["r1"]!)
let r2 = Int(snapshotValue["r2"]!)
let r3 = Int(snapshotValue["r3"]!)
let classification = snapshotValue["classification"]!
let allTheLikes = likeclass()
allTheLikes.discountID = businessID!
allTheLikes.businessName = businessName
allTheLikes.dateApplied = DateNumber!
allTheLikes.theDeal = theDeal
allTheLikes.phoneNumber = phoneNumber
allTheLikes.imageName = imageName
allTheLikes.dateText = dateText
allTheLikes.numberNumber = phoneNumberInteger!
allTheLikes.companylogo = companyLogo
allTheLikes.r1 = r1!
allTheLikes.r2 = r2!
allTheLikes.r3 = r3!
allTheLikes.classification = classification
self.theLikeArray.append(allTheLikes)
}
print(theLikeArray)
}
func updateLikeDatabase(){
for i in 0...allDiscounts.list.count-1{
let likesDB = Database.database().reference().child("Discounts")
let likeDictionary = ["BusinessID": "\(i)","businessName":"\(allDiscounts.list[i].businessName)","DateNumber": "\(allDiscounts.list[i].dateApplied)","theDeal": "\(allDiscounts.list[i].theDeal)" ,"PhoneNumberText": "\(allDiscounts.list[i].phoneNumber)","ImageName": "\(allDiscounts.list[i].imageName)","DateText": "\(allDiscounts.list[i].dateText)" ,"phoneNumberInteger": "\(allDiscounts.list[i].numberNumber)","companyLogo": "\(allDiscounts.list[i].companylogo)","r1": "\(allDiscounts.list[i].r1)" ,"r2": "\(allDiscounts.list[i].r2)","r3": "\(allDiscounts.list[i].r3)","classification": "\(allDiscounts.list[i].classification)"] as [String : String]
likesDB.child("\(allDiscounts.list[i].businessName)").setValue(likeDictionary) {
(error, reference) in
if error != nil{
let alert = UIAlertController(title: "Error", message: "There was an error registering your like. Reconnect online and try again", preferredStyle: .alert)
let okAction = UIAlertAction(title: "Ok", style: .default, handler: nil)
alert.addAction(okAction)
self.present(alert,animated: true)
// self.showerror()
}
else{
print("Message Saved Successfully")
}
}
}
}
解决方案
数据可能必须从 Firebase 服务器下载。由于这可能需要一些时间,因此该数据是异步加载的。Firebase 不会阻止您的主代码(并使您的应用程序无响应),而是允许您的主代码继续运行,并在数据可用时调用您的完成处理程序。
这意味着任何需要数据库数据的代码都必须在完成处理程序中。
所以在你的情况下是这样的:
let likesDB = Database.database().reference().child("Discounts")
likesDB.observe(.childAdded) { (snapshot) in
let snapshotValue = snapshot.value as! Dictionary<String , String>
let businessID = Int(snapshotValue["BusinessID"]!)
let businessName = snapshotValue["businessName"]!
let DateNumber = Int(snapshotValue["DateNumber"]!)
let theDeal = snapshotValue["theDeal"]!
let phoneNumber = snapshotValue["PhoneNumberText"]!
let imageName = snapshotValue["ImageName"]!
let dateText = snapshotValue["DateText"]!
let phoneNumberInteger = Int(snapshotValue["phoneNumberInteger"]!)
let companyLogo = snapshotValue["companyLogo"]!
let r1 = Int(snapshotValue["r1"]!)
let r2 = Int(snapshotValue["r2"]!)
let r3 = Int(snapshotValue["r3"]!)
let classification = snapshotValue["classification"]!
let allTheLikes = likeclass()
allTheLikes.discountID = businessID!
allTheLikes.businessName = businessName
allTheLikes.dateApplied = DateNumber!
allTheLikes.theDeal = theDeal
allTheLikes.phoneNumber = phoneNumber
allTheLikes.imageName = imageName
allTheLikes.dateText = dateText
allTheLikes.numberNumber = phoneNumberInteger!
allTheLikes.companylogo = companyLogo
allTheLikes.r1 = r1!
allTheLikes.r2 = r2!
allTheLikes.r3 = r3!
allTheLikes.classification = classification
self.theLikeArray.append(allTheLikes)
print(theLikeArray)
}
请注意,这是一个令人难以置信的常见混淆来源,因此我强烈建议您阅读有关该主题的其他一些问题:
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