为什么我的从数据库中提取信息的函数不起作用? [英] Why isn't my function that pulls information from the database working?
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.这两个函数都在我的 viewDidLoad(); 中调用，但是，即使我的数据库已完全填充，print(theLikeArray) 也返回空括号.
I am trying to pull a list of data from my Firebase Database. Below is my code. Both functions are called in my viewDidLoad(); however, the print(theLikeArray) is returning empty brackets even though my database is fully populated.
以下是我目前使用的代码.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被调用.
Below is the code I am currently using. The first function is used to retrieve all the information from the database while the second is used to populate the database. The second function is called prior to the first.
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")
}
}
}
}
推荐答案
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.
The data may have to be downloaded from the Firebase servers. Since this may take some time, that data is loaded asynchronously. Instead of blocking your main code (and making your app unresponsive), Firebase allows your main code to continue, and calls your completion handler when the data is available.
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.
All this means is that any code that needs the data from the database must be inside the completion handler.
所以在你的情况下是这样的:
So in your case something like:
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，这是一个非常常见的混淆来源，因此我强烈建议您阅读有关该主题的其他一些问题:
Note that this is an incredibly common source of confusion, so I highly recommend that you read some other questions on the topic:
- Swift 函数从异步 firebase 调用返回值
- 这是显示异步数据的好方法吗?
- 使用 Firebase 异步编写代码
- 数据库提取仅存在于其自身的函数中
- 在加载数据之前完成所有异步请求?
- 快速访问闭包外的数据
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