How can I store an array of custom objects (Goals)

Question

How can I store an array of objects of type Goal which I have created in NSUserDefaults? (in swift)

Here is the code:

func saveGoalList ( newGoalList         


        

Answer 1

For Swift 2.1, your Goal class should look like :

import Foundation

class Goal : NSObject, NSCoding {

    var title: String

    // designated initializer
    init(title: String) {
        self.title = title

        super.init()        // call NSObject's init method
    }

    // MARK: - comply wiht NSCoding protocol

    func encodeWithCoder(aCoder: NSCoder) {
        aCoder.encodeObject(title, forKey: "GoalTitle")
    }

    required convenience init?(coder aDecoder: NSCoder) {
        // decoding could fail, for example when no Blog was saved before calling decode
        guard let unarchivedGoalTitle = aDecoder.decodeObjectForKey("GoalTitle") as? String
            else {
                // option 1 : return an default Blog
                self.init(title: "unknown")
                return

                // option 2 : return nil, and handle the error at higher level
        }

        // convenience init must call the designated init
        self.init(title: unarchivedGoalTitle)
    }
}

and you should use it in your view controller like I did in this test code :

    // create an array with test data
    let goal1 = Goal(title: "first goal")
    let goal2 = Goal(title: "second goal")
    let goalArray = [goal1, goal2]

    // first convert the array of custom Goal objects to a NSData blob, as NSUserDefaults cannot handle arrays of custom objects directly
    let dataBlob = NSKeyedArchiver.archivedDataWithRootObject(goalArray)

    // this NSData object can now be stored in the user defaults
    NSUserDefaults.standardUserDefaults().setObject(dataBlob, forKey: "myGoals")

    // sync to make sure they are saved before we retreive anytying
    NSUserDefaults.standardUserDefaults().synchronize()

    // now read back
    if let decodedNSDataBlob = NSUserDefaults.standardUserDefaults().objectForKey("myGoals") as? NSData {
        if let loadedGoalsArray = NSKeyedUnarchiver.unarchiveObjectWithData(decodedNSDataBlob) as? [Goal] {
            for goal in loadedGoalsArray {
                print("goal : \(goal.title)")
            }
        }
    }

As a final remark : it would be easier to use NSKeyedArchiver instead of NSUserDefaults, and store your array of custom objects directly to a file. You can read more about the difference between both methods in another answer I posted here.