我正在尝试在Firebase上获取字符串（在对象内部）（使用Swift）
let currentDocument = db.collection("countries").document("United States")
currentDocument.getDocument { (document, error) in
if let document = document, document.exists {
let cities = document.data()!["cities"] as? [AnyObject] // This grabs data from a Firebase object named `cities`, inside the object there are arrays that have two pieces of data (e.g. ["cityName" : "New York", "currentTemperature" : 38])
for i in 0..<cities!.count {
let cityName = String(cities![i]["cityName"]!) // Here is where I get the error `Cannot invoke initializer for type 'String' with an argument list of type '(RemoteConfigValue)'`
}
} else {
print("Document does not exist")
}
}
搜索此错误后，我发现的常规解决方案类似于these ones
但是，即使在应用了这些解决方案之后，例如：
if let cityName = cities![i]["cityName"]! as? String {
print(cityName)
}
我仍然收到类似
Cast from 'RemoteConfigValue' to unrelated type 'String' always fails的错误我该如何解决？
最佳答案
请阅读documentation
class RemoteConfigValue : NSObject, NSCopying
此类为Remote Config参数值提供了包装，并提供了以不同数据类型获取参数值的方法。
所以你必须写这样的东西
if let cities = document.data()!["cities"] as? [[String:Any]] { // cities is obviously an array of dictionaries
for city in cities { // don't use index based loops if you actually don't need the index
if let cityName = city["cityName"] as? RemoteConfigValue {
print(cityName.stringValue)
}
}
}