I am accessing user default value as:
let data = UserDefaults.standard.object(forKey: identifier)
when I see the value in data it is visible as:
https://i.stack.imgur.com/UOjI8.png
type of data is
po type(of: data)
Swift.Optional<Any> . //Output
How can I access pageNumber?
since data is a dictionary in order to have access to pageNumber you need to cast data as a Dictionary
guard let data = UserDefaults.standard.value(forKey: identifier) as? [String: Any] else { //fallback here if you need return }
let pageNumber = data["pageNumber"] as? Int ?? 0
Simply use dictionary(forKey:) method on UserDefaults instance to directly fetch a dictionary from UserDefaults.
The dictionary returned is of type [String:Any]?
if let dict = UserDefaults.standard.dictionary(forKey: identifier) {
let pageNumber = dict["pageNumber"] as? Int
}
Note: pageNumber is of type Int?. Unwrap it to use further.
Related
I have this code
let jsonData = try JSONSerialization.jsonObject(with: data, options: []) as! [Any?]
if var first = jsonData[0] as! String?{
if(first=="Error"){
DispatchQueue.main.async(execute: {
self.postNotFoundLabel.isHidden = false
});
}else if(first=="Empty"){
print("Empty")
}
}
What i want to do is to cast jsonData[0] to String if it's possible and if it's not then move on.But instead when it's not possible application stops and gives me an error
Could not cast value of type '__NSDictionaryI' (0x1092054d8) to 'NSString' (0x108644508).
How can i cast only when it's possible?
You are trying to force-cast to an optional String. That's not what you want.
Change:
if var first = jsonData[0] as! String? {
to:
if var first = jsonData[0] as? String {
This tries to cast to String. If jsonData[0] isn't actually a String, you get nil and the if var fails.
And you probably want if let, not if var since you don't seem to be making any change to first.
First of all JSON objects will never return optional values so [Any?] is nonsense.
Second of all the error message says the type cast to string is inappropriate because the type of the result is actually a dictionary.
Solution: Check the type for both String and Dictionary
if let jsonData = try JSONSerialization.jsonObject(with: data) as? [Any],
let first = jsonData.first {
if let firstIsDictionary = first as? [String:Any] {
// handle case dictionary
} else if let firstIsString = first as? String {
// handle case string
}
}
PS: A type cast forced unwrap optional to optional (as! String?) is nonsense, too.
Here's the Swifty way to do what you're doing :)
guard let jsonData = try JSONSerialization.jsonObject(with: data, options: []) as? [Any?], let first = jsonData[0] as? String else {
DispatchQueue.main.async(execute: {
self.postNotFoundLabel.isHidden = false
});
return
}
if(first == "Empty") {
print(first)
}
Don't use as! if you are not sure that casting will succeed. The exclamation mark after the as keyword forces the casting, which throws an error if the casting does not succeed.
Use as? instead, which returns an optional variable of the type you were trying to casting to. If the casting fails, instead of throwing an error, it just returns nil.
let jsonData = try JSONSerialization.jsonObject(with: data) as? [Any]
if var first = jsonData.first as? String{
if(first=="Error"){
DispatchQueue.main.async(execute: {
self.postNotFoundLabel.isHidden = false
});
}else if(first=="Empty"){
print("Empty")
}
}
Everything works swimmingly except for when I do a random string like "fds", how would I correctly and efficiently use a guard to protect from this sort of error?
init(weatherData: [String: AnyObject]) {
city = weatherData["name"] as! String
let weatherDict = weatherData["weather"]![0] as! [String: AnyObject]
description = weatherDict["description"] as! String
icon = weatherDict["icon"] as! String
let mainDict = weatherData["main"] as! [String: AnyObject]
currentTemp = mainDict["temp"] as! Double
humidity = mainDict["humidity"] as! Int
let windDict = weatherData["wind"] as! [String: AnyObject]
windSpeed = windDict["speed"] as! Double
}
how would I correctly and efficiently use a guard to protect from this sort of error?
Why would you want to? If the caller does not hand you a dictionary whose "name" key is present and is a string, you are dead in the water because you cannot initialize city. You want to crash.
If you would like to escape from this situation without actually crashing, then make this a failable initializer and fail (return nil) if the dictionary doesn't contain the needed data. This effectively pushes the danger of crashing onto the caller, because the result will be an Optional that might be nil, and the caller must check for that.
init?(weatherData: [String: AnyObject]) {
guard let city = weatherData["name"] as? String else {return nil}
self.city = city
// ... and so on ...
}
But what I would do is none of those things. I would rewrite the initializer as init(city:description:icon:currentTemp:humidity:windSpeed:) and force the caller to parse the dictionary into the needed data. That way, if the data is not there, we don't even try to initialize this class in the first place. My argument would be that it is the caller's job to parse the dictionary; this class should have no knowledge of the structure of some complex dictionary pulled off the Internet (or whatever the source is).
I am on point where I gotta compare non optional value with nil. But I can't do it because Xcode says:
Comparing non-optional value of type 'Int' to nil always returns false
So I created Struct and then made variable: var products: [Product] = []
How I am able to compare it with nil?:
if products[indexPath.row].snusPortions == nil
{
cell.snusPortionsAmountLabel.text = "N/A"
}else
{
cell.snusPortionsAmountLabel.text = String(products[indexPath.row].snusPortions)
}
I've assigned values to them like this:
let ref = FIRDatabase.database().reference().child("Snuses").queryOrdered(byChild: "Brand").queryEqual(toValue: brandName)
ref.observeSingleEvent(of: .value, with: { (snapshot) in
if snapshot.exists(){
let enumerator = snapshot.children
while let thisProduct = enumerator.nextObject() as? FIRDataSnapshot
{
print(thisProduct.value) // So I may see what the data is like and know how to extract it
// Chances are you'd have to create a dictionary
let thisProductDict = thisProduct.value as! [String:AnyObject]
let productName = thisProductDict["Products"] as! String
let snusPortions = thisProductDict["PortionsCan"] as? Int
let productObject = Product(snusProductTitle: productName, snusNicotine: snusNicotine, snusPortions: snusPortions!, snusFlavor: snusFlavor, snusWeight: snusWeight!, snusShippingWeight: snusShippingWeight, snusProductImageURL: productURL)
self.products.append(productObject)
print(self.products)
}
self.tableView.reloadData()
}
})
This is Product struct:
struct Product {
var snusProductTitle: String
init()
{
snusProductTitle = ""
}
init(snusProductTitle: String){
self.snusProductTitle = snusProductTitle
}
}
While testing it says snusPortions is nil but I said to make it "N/A" if it is nil, why?
It sounds like you are confusing yourself between the local variable snusPortions and the Product property snusPortions.
In your Product definition, the property snusPortions is an Int. It can never be nil. Hence, in this code:
if products[indexPath.row].snusPortions == nil
... this Product's snusPortions will never be nil, and we will never set the text to "N/A".
Now let's look at your other code:
let snusPortions = thisProductDict["PortionsCan"] as? Int
This is a completely different snusPortions. It can be nil, namely, if thisProductDict lacks a "PortionsCan" key or if its value is not castable to Int.
I am using xmartlabs/Eureka to build an app with a dynamic form.
In order to fill the form I have to use setValues(values: [String: Any?]).
But I have the form values in an NSDictionary variable and I cannot cast it to [String:Any?].
Is there a way to convert an NSDictionary to [String:Any?] ?
Just an example:
if let content = data["data"] as? [String:AnyObject] {
print(content)
}
The data is a JSON object here. Use it accordingly.
Hope this helps:
let dict = NSDictionary()
var anyDict = [String: Any?]()
for (value, key) in dict {
anyDict[key as! String] = value
}
I have a segment of code that gets info from an API, and I need to add it to a Dictionary. The code is below:
typealias JSONdic = [String: AnyObject]
var weatherData: AnyObject = StorageManager.getValue(StorageManager.StorageKeys.WeatherData)!
let json: AnyObject = ["Any": "Object"]
if let json = json as? JSONdic, history = json["history"] as? JSONdic, tempi = history["tempi"] as? Int, hum = history["hum"] as? String, precip = history["precipi"] as? String{
println("Temperature:\(tempi) Humidity:\(hum) Precipitation:\(precip)")
weatherData = [NSDate: AnyObject]()
let temp = tempi as NSNumber
weatherData[(The Current Date)] = temp
}
I want to first add "temp" to the weatherData Dictionary, but even after casting it to NSNumber, I am told that an NSNumber value cannot be assigned to the AnyObject?! type. Can anyone help me fix this?
Your weatherData variable is of type AnyObject. Despite the fact that you later assign it a value of type [NSDate: AnyObject], the variable itself is still considered by the compiler to be AnyObject. You then hit problems because you try to subscript it, assigning an NSNumber, which is obviously not possible on AnyObject.
Your declaration of weatherData should ensure it is the type you intend. If you are sure that your StorageManager will return you the appropriate dictionary type for the weather data key, you can force downcast it to the correct type:
var weatherData = StorageManager.getValue(StorageManager.StorageKeys.WeatherData) as! [NSDate: NSObject]