(Swift) Storing and retrieving Array to NSUserDefa

问题:

I am trying to store an array to NSUserDefaults and retrieve the array when needed to populate a UITableView.

Currently I am using:

//store data
NSUserDefaults.standardUserDefaults().setObject(myArray, forKey: "\(identity.text!)listA")                    
NSUserDefaults.standardUserDefaults().synchronize()

//retrieve data
let tabledata = NSUserDefaults.standardUserDefaults().stringForKey("\(identity.text!)listA")
myArray = [tabledata!]
tableView.reloadData()

But I get

fatal error: unexpectedly found nil while unwrapping an Optional value

when trying to load the data. I am not sure if the issue is in the storage or the retrieval. Has anyone been through this before?

回答1:

From your code I see you are storing some array

// Your code
NSUserDefaults.standardUserDefaults().setObject(myArray, forKey: "\(identity.text!)listA")

and retrieving a string

//Your code
let tabledata = NSUserDefaults.standardUserDefaults().stringForKey("\(identity.text!)listA")

There is probably a type mismatch, You store one type and retrieve another type.

While retrieving either use arrayForKey() or objectForKey() see the code below.

let tabledata = NSUserDefaults.standardUserDefaults().arrayForKey("\(identity.text!)listA") 

or

let tabledata = NSUserDefaults.standardUserDefaults().objectForKey("\(identity.text!)listA")

If it is an array I would go with First one.

回答2:

Here are the way that you can store and retrieved array of object with help of NSKeyArchive.

To Store array to NSUserDefault.

let placesData = NSKeyedArchiver.archivedData(withRootObject: placesArray)
UserDefaults.standard.set(placesData, forKey: "places")

To Retrieved array from NSUserDefault.

let placesData = UserDefaults.standard.object(forKey: "places") as? NSData

if let placesData = placesData {
    let placesArray = NSKeyedUnarchiver.unarchiveObject(with: placesData as Data) as? [Place]
    print(placesArray)
}

Hope this help you.

回答3:

I came to this question looking how to save a String array to UserDefaults but didn't find a clear answer here. However, I did find the answer in How to save user settings using NSUserDefaults. Read that article for more information.

Saving and Retrieving a String array to UserDefaults

Save array

let array = ["horse", "cow", "camel", "sheep", "goat"]

let defaults = UserDefaults.standard
defaults.set(array, forKey: "SavedStringArray")

Retrieve array

let defaults = UserDefaults.standard
let array = defaults.object(forKey: "SavedStringArray") as? [String] ?? [String]()

回答4:

What are you storing in the array?

If it's objects it won't work, if It's just strings or numbers then it should be fine.

Next steps you take should be to turn on exception breakpoints and maybe println() everything you can so you can pinpoint the exact whereabouts of the problem.

As a shot in the dark I would suggest maybe (identity.text!) is coming out as nil

Also you should probably change it to this

if let tabledata: NSArray = NSUserDefaults.standardUserDefaults().stringForKey("\(identity.text!)listA"){

    myArray = [tabledata!]

    tableView.reloadData()
}

This will make the code not even try to run unless there is a value it can use

回答5:

Latest swift3 version to store array of data into userdefaults and get that array of data using keys

    let nameArray = ["Ramu","JAGAN","Steve","Swift"]
    let namesArrayData = NSKeyedArchiver.archivedData(withRootObject: nameArray)
    UserDefaults.standard.set(namesArrayData, forKey: "arrayData")

RetriveData

        let retriveArrayData= UserDefaults.standard.object(forKey:  "arrayData") as? NSData

   if let retriveArrayData= namesArrayData{
  let retriveArray = NSKeyedUnarchiver.unarchiveObject(with: namesArraydata as Data) as? [nameArray]
  print(retriveArray )
}

回答6:

This has been changed in swift 3. Note that this works with device but not playground or simulator

//store the array
let array = ["horse", "cow", "camel", "sheep", "goat"]

let defaults = UserDefaults.standard

defaults.setValue(array, forKey: "history")

defaults.synchronize()

//Retrieve the array
if((UserDefaults.standard.array(forKey: "history")) != nil){
    let historyWords = (UserDefaults.standard.array(forKey: "history") as? [String])!
    print(historyWords)
}

回答7:

Store into User Default:

let arrayFruit = ["Apple","Banana","Orange","Grapes","Watermelon"]    
 //store in user default
UserDefaults.standard.set(arrayFruit, forKey: "arrayFruit")

Retrieving array from User Defaults:

if let arr = UserDefaults.standard.array(forKey: "arrayFruit") as? [String]{
    print(arr)
}