CODEWITHSUNDEEP
iosswiftnsuserdefaults
TangZijian
TangZijian

Reputation: 354

NSUserDefaults unreliable?

I am using NSUserDefaults to store key/value pairs in my application. Below is the sample code:

override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(animated)
    let ud = NSUserDefaults.standardUserDefaults()
    if !(ud.boolForKey("launched_before")) {
        print("first_launch")
        ud.setBool(true, forKey: "launched_before")
    } else {
        print("not_first_launch")
    }
}

The first time I launch the application, it prints "first_launch" as expected, and the second time I launch the application, it prints "not_first_launch" as expected too. However, if I continue re-launching the application by pressing Stop and Run button in the Xcode after a few times (maybe 4 to 20 times), the boolForKey("launched_before") will return false, which is wrong.
I am testing on my device (iPhone 6, iOS 9.3.1) and Xcode 7.3.
Anyone can help me?

Upvotes: 3

Views: 219

Answers (1)

Sean Lintern
Sean Lintern

Reputation: 3141

NSUserDefaults does save unreliably, even worse that your just terminating it through Xcode stop/run.

Calling NSUserDefaults.StandardUserDefaults().synchronize will save the data.

Upvotes: 4

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