[英]Can't pass variable value from firebase firestore to another class SWIFT
所以我在 class Functions
中有这个 function :
struct Prices {
var standardPrice: Int!
}
// FUNC PRICING
class Functions {
private var PricingRef: CollectionReference!
var price = Prices()
func getPrice() -> Prices {
PricingRef = Firestore.firestore().collection("ProductXYZ")
PricingRef.getDocuments { (snapshot, error) in
if let err = error {
debugPrint("Error fetching data \(err)")
}
else {
guard let snap = snapshot else { return }
for document in snap.documents {
let data = document.data()
let std = data["standard"] as! String
self.price.standardPrice = Int(std)!
print(self.price.standardPrice!) // This print the intended result
}
}
}
return price
}
}
然后我想将standardPrice
值传递给这个 class,称为PriceList
:
class PriceList: UITableViewController {
var price = Prices()
var newStandardPrice = 0
func Price() {
price = Functions().getPrice()
newStandardPrice = price.standardPrice // always error with value nil
}
我总是有newStandardPrice
为零的错误。 但是print(self.price.standardPrice!)
显示了我想要的结果数量。 据我所知,这里的问题是因为 firebase 火库从数据库中获取数据需要时间。 从 firebase 数据库中分配新价格后,如何获取standardPrice
的值?
任何帮助将不胜感激
谢谢
您需要使用完成处理程序,因为它的异步 function
func getPrice(completion:@escaping (Prices?,Error?)-> Void) {
PricingRef = Firestore.firestore().collection("ProductXYZ")
PricingRef.getDocuments { (snapshot, error) in
if let err = error {
debugPrint("Error fetching data \(err)")
completion(nil,err)
}
else {
guard let snap = snapshot else { return }
for document in snap.documents {
let data = document.data()
let std = data["standard"] as! String
self.price.standardPrice = Int(std)!
print(self.price.standardPrice!) // This print the intended result
completion(self.price.standardPrice,nil)
}
}
}
}
如何使用
Functions().getPrice { (price, error) in
if let err = error {
// do something if you get error
} else if let getPrice = price {
// use price
self.price = getPriice
}
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