Core Motion Swift Closure issue

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I'm trying to convert an old game application built in obj-c to the new swift code. i'm having some issues understanding swift closures and how to use them for example in the"startAccelerometerUpdatesToQueue" method.

i have initialized the motion manager in this way

motionManager!.accelerometerUpdateInterval = (1/40)

then in the viewdidload of my view controller

var queue:NSOperationQueue
motionManager?.startAccelerometerUpdatesToQueue(queue, withHandler: {(accelerometerData :     CMAccelerometerData, error : NSError) in


})

the "startAccelerometerUpdatesToQueue" is giving me an error and i'm pretty sure i didn't understand the correct closure syntax.

Any ideas?

Actually, you just got the signature wrong – the arguments to your closure need to be optionals (since they are passed from Objective-C, they could be nil). Because of that, the arguments you provide don't match an existing method signature, and because of that you get an error.

Take a look at the iOS 8 API docs, they also provide Swift signatures:

func startAccelerometerUpdatesToQueue(_ queue: NSOperationQueue!,
                          withHandler handler: CMAccelerometerHandler!)

and CMAccelerometerHandler is defined as

typealias CMAccelerometerHandler = (CMAccelerometerData!, NSError!) -> Void

Thus, your call should be:

motionManager?.startAccelerometerUpdatesToQueue(queue, withHandler: {(accelerometerData :     CMAccelerometerData!, error : NSError!) in


})

And as with any function/method that takes a closure as it's last argument, you can leave it out of the argument list and write it after the call (trailing closure syntax – this example also leaves out the types, as they can be inferred, but that is optional):

motionManager?.startAccelerometerUpdatesToQueue(queue) { accelerometerData, error in

}

Core Motion Swift Closure issue, i'm having some issues understanding swift closures and how to use them for example in the"startAccelerometerUpdatesToQueue" method. i have initialized the  Closures in Swift are similar to blocks in C and Objective-C and to lambdas in other programming languages. Closures can capture and store references to any constants and variables from the context in which they are defined. This is known as closing over those constants and variables. Swift handles all of the memory management of capturing for you.

Beginning iPhone Development with Swift 2: Exploring the iOS SDK, Swift closures, 540 system architecture, 539 ViewController.swift, 570 Gyroscope vs. accelerometer, 712 attitude results, 721 core motion (see Core motion)  Closures in Swift 4 are similar to that of self-contained functions organized as blocks and called anywhere like C and Objective C languages. Constants and variable references defined inside the functions are captured and stored in closures.

import UIKit
import CoreMotion

class ViewController: UIViewController {

    let motionManager = CMMotionManager()
    var timer: Timer!

    override func viewDidLoad() {
        super.viewDidLoad()

        motionManager.startAccelerometerUpdates()
        motionManager.startGyroUpdates()
        motionManager.startMagnetometerUpdates()
        motionManager.startDeviceMotionUpdates()

        timer = Timer.scheduledTimer(timeInterval: 3.0, target: self, selector: #selector(ViewController.update), userInfo: nil, repeats: true)
    }

    @objc func update() {

        if let accelerometerData = motionManager.accelerometerData {
            print(accelerometerData)
        }
        if let gyroData = motionManager.gyroData {
            print(gyroData)
        }
        if let magnetometerData = motionManager.magnetometerData {
            print(magnetometerData)
        }
        if let deviceMotion = motionManager.deviceMotion {
            print(deviceMotion)
        }
    }

}

Core Motion and Core Location: Learn how to detect the user's , Learn how to detect the user's location in iOS 11 with Swift 4 JD Gauchat Fortunately, Core Motion was designed to help us with these tasks. One of and the withHandler attribute is the closure that is going to process the values returned. Swift Closure can be used to capture and store the state of some variable at a particular point in time and use it later(We’ll be discussing this at length later in the tutorial) Closures allow us to run a piece of code even after the function has returned; Swift Closure Syntax. Let’s recall the syntax of Functions in swift first.

Core Motion and Core Location in iOS 12: Learn how to detect the , Learn how to detect the user's location in iOS 12 with Swift 4.2 J.D Gauchat Fortunately, Core Motion was designed to help us with these tasks. One of and the withHandler attribute is the closure that is going to process the values returned. 3 Core Motion Swift Closure issue Jun 10 '14. 2 MKMapView addAnnotations crash Sep 25 '14. 2 PFInstallation app first launch issue Oct 26 '14. 2 iOS App Crash on view

How Can I Solve An EXC_BAD_ACCESS …, How Can I Solve An EXC_BAD_ACCESS That Occurs Within the CoreMotion of IOS a problem where I experience an occasional EXC_BAD_ACCESS crash that run loop is trying to invoke a block of code (a closure, it's called in Swift). Core Motion in iOS using Swift. Users generate motion events when they move, shake, or tilt the device. These motion events are detected by the device hardware, specifically, the accelerometer and the gyroscope. The Core Motion framework lets your application receive motion data from the device hardware and process that data.

Beginning iPhone Development with Swift 3: Exploring the iOS SDK, attitudeLabel.text = attitudeText } } } } } First, we import the Core Motion work to be done, as specified by the closure you will give it, each time an event occurs. Core Motion reports motion- and environment-related data from the onboard hardware of iOS devices, including from the accelerometers and gyroscopes, and from the pedometer, magnetometer, and barometer. You use this framework to access hardware-generated data so that you can use it in your app.