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NSCoding Tutorial for iOS: How To Save Your App Data

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An NSCoding tutorial on how to quickly and easily save your app's data with NSCoding and NSFileManager in iOS.

This is a companion discussion topic for the original entry at https://www.raywenderlich.com/3111-nscoding-tutorial-for-ios-how-to-save-your-app-data
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I think I must be dense, but I am having a hard time understanding how to store more than one thing at a time in an NSCoder.

My app keeps an internal running history of dice rolls, and what I’m trying to do is enable the saving or loading of saved histories.

I can get one, if I try to store the next, I get a message about the new values clobbering the older ones.

Here’s what I’ve got so far:

func encodeWithCoder(aCoder: NSCoder) {
	
	for stackItem in 0..<self.abilityScoreHistoryStack.count {
		
		for roll in 0..<self.abilityScoreHistoryStack[stackItem].rolls.count {
			
			aCoder.encodeInteger(self.abilityScoreHistoryStack[stackItem].rolls[roll], forKey: PropertyKey.rollsKey)
			
		}
		aCoder.encodeInteger(self.abilityScoreHistoryStack[stackItem].numberOfDice, forKey: PropertyKey.numDiceKey)
		aCoder.encodeInteger(self.abilityScoreHistoryStack[stackItem].sizeOfDice, forKey: PropertyKey.dieSizeKey)
		aCoder.encodeInteger(self.abilityScoreHistoryStack[stackItem].droppedDice, forKey: PropertyKey.droppedKey)
		aCoder.encodeInteger(self.abilityScoreHistoryStack[stackItem].modifier, forKey: PropertyKey.modKey)
		aCoder.encodeObject(self.abilityScoreHistoryStack[stackItem].itemTitle, forKey: PropertyKey.itemtitleKey)
		aCoder.encodeBool(self.abilityScoreHistoryStack[stackItem].rollSortStatus, forKey: PropertyKey.rollSortStatusKey)
		
	}
	
	
	
	
}

and to trigger it, in the view controller (and triggered by a tap on a button):

@IBAction func saveHistoryButtonAction(sender: UIButton) {
	
	for _ in 0..<self.charGen.abilityScoreHistoryStack.count {
	
		saveHistory()
		
	}
	
}
// MARK: NSCoding
func saveHistory () {
	
	let isSuccessfulSave = NSKeyedArchiver.archiveRootObject(self.charGen, toFile: CharacterGenerator.ArchiveURL.path!)
	
	if (!isSuccessfulSave) { print("Save failed. Try something different") }
	// else {  }
	
}

I think I understand why I’m getting message that the new values clobber the old, but I am having a devil of a time thinking of another way to handle the fact that there’s an array of these rolls (the history stack is an array of structs defined in the class).

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This tutorial is more than six months old so questions are no longer supported at the moment for it. We will update it as soon as possible. Thank you! :]