Wrapper to execute code only once

Once.swift

//
//  Once.swift
//
//  Created by Patrick Kladek on 28.01.20.
//

import Foundation


/// `doOnce` Block can be called multiple times but will only run one time.
class Once: NSObject {

    private var didRun: Bool

    // MARK: - Lifecycle

    override init() {
        self.didRun = false
    }

    // MARK: Once

    func doOnce(block: () -> Void) {
        guard self.didRun == false else { return }

        block()
        self.didRun = true
    }

    func reset() {
        self.didRun = false
    }
}




/// Exmaple usage

// Add this as property to your class
let setupScrollPosition = Once()


// Somewhere in a function
override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    self.setupScrollPosition.doOnce {
        // Do setup that should only run one time
    }
}