为什么我从数据库中提取信息的功能不起作用? [英] Why isn't my function that pulls information from the database working?
问题描述
我正在尝试从Firebase数据库中提取数据列表.下面是我的代码.在我的viewDidLoad();中都调用了这两个函数，但是即使我的数据库已完全填充，print(theLikeArray)仍返回空括号.
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.
以下是我当前正在使用的代码.第一个函数用于从数据库检索所有信息，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
可能必须从Firebase服务器下载数据.由于这可能需要一些时间，因此该数据是异步加载的. Firebase不会阻止您的主要代码(并使您的应用程序无响应)，而是允许您的主要代码继续运行，并在数据可用时调用完成处理程序.
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.
这意味着所有需要数据库中数据的代码都必须在完成处理程序内部 .
All this means is that any code that needs the data from the database must be inside the completion handler.
因此，您的情况如下:
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:
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调用中返回值
- 这是显示异步数据的好方法吗? /a>
- 使代码与Firebase异步
- 数据库提取仅存在于其自身的功能中
- 在加载数据之前完成所有异步请求吗?
- 在闭包之外快速访问数据
- Swift Function returning a value from asynchronous firebase call
- Is this a good way to display asynchronous data?
- Make code with Firebase asynchronous
- Database fetch exists only in its own function
- Finish all asynchronous requests before loading data?
- Swift access data outside closure
这篇关于为什么我从数据库中提取信息的功能不起作用?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
