Implementation example of Review Request in iOS.

ReviewRequestManager.swift

//
//  ReviewRequestManager.swift
//
//  Created by yosshi4486 on 2021/07/22.
//

import StoreKit

/// The global variable to get current app version.
///
/// This variable should move under an apporopriate type if it is found.
var currentAppVersion: String? {

    // Get the current app version.
    let infoDictionaryKey = "CFBundleShortVersionString"
    guard
        let currentVersion = Bundle.main.object(forInfoDictionaryKey: infoDictionaryKey) as? String
    else {
        fatalError("Expected to find a app version in the info dictionary")
    }
    return currentVersion

}

/// A manager of review request.
///
/// *Review Request Manager* folllows best practice, which apple documentation describes at [Requesting App Store Reviews](https://developer.apple.com/documentation/storekit/requesting_app_store_reviews)
/// and Human Interface Guideline describes at [Ratings and Reviews](https://developer.apple.com/design/human-interface-guidelines/ios/system-capabilities/ratings-and-reviews/).
class ReviewRequestManager {

    enum ReviewConditionStorageKey: String {
        case processCompletedCountKey
        case lastVersionPromptedForReviewKey
    }

    /// The local key value storage to store review related information.
    var userDefault: UserDefaults = .standard

    /// The integer value that counts how many times does user tap done button at navigation bar.
    var processCompletedCount: Int {
        get {
            // If the count has not yet been stored, this will return 0.
            return userDefault.integer(forKey: ReviewConditionStorageKey.processCompletedCountKey.rawValue)
        }

        set {
            userDefault.set(newValue, forKey: ReviewConditionStorageKey.processCompletedCountKey.rawValue)
        }
    }

    /// The string value that represents app version, which this app showed prompt at last.
    var lastVersionPromptedForReview: String? {
        get {
            // If the version has not yet been stored, this will return nil.
            return userDefault.string(forKey: ReviewConditionStorageKey.lastVersionPromptedForReviewKey.rawValue)
        }

        set {
            userDefault.set(newValue, forKey: ReviewConditionStorageKey.lastVersionPromptedForReviewKey.rawValue)
        }
    }

    /// The current version of this app.
    var currentAppVersion: String?

    /// The threthold value to determine whether this app can request review to ther user.
    var thretholdCountForReviewRequest: Int = 10

    /// The waittime value to determine whether the user is continuing to perform tasks.
    var waitTimeForReviewRequest: Double = 3.0

    /// The bool value whether this app can request app review to the user.
    var canRequestReview: Bool {
        print("Process completed \(processCompletedCount) time(s)")
        print("Current app version: \(currentAppVersion ?? "nil")")
        return processCompletedCount >= thretholdCountForReviewRequest && currentAppVersion != lastVersionPromptedForReview
    }

    /// The work item, which stores request of app store review.
    ///
    /// The work item is used to protect multiple request at same time.
    var requestReviewWorkItem: DispatchWorkItem? = nil

    init(userDefaults: UserDefaults = .standard, currentAppVersion: String?, thretholdCountForReviewRequest: Int = 10, waitTimeForReviewRequest: Double = 3.0) {
        self.userDefault = userDefaults
        self.currentAppVersion = currentAppVersion
        self.thretholdCountForReviewRequest = thretholdCountForReviewRequest
        self.waitTimeForReviewRequest = waitTimeForReviewRequest
    }

    /// Increments the count of process completed, which means adding 1 to its value.
    func incrementProcessCompletedCount() {
        processCompletedCount += 1
    }

    /// Requests review for this app if the provided condition returns true.
    ///
    /// You must use this method after checking `canRequestReview` and it returns true like bellow:
    ///
    ///     if requestReviewManager.canRequestReview {
    ///         requestReviewManager.requestReview(in: view.window!.windowScene!) {
    ///             // Do something
    ///             return true
    ///         }
    ///     }
    ///
    /// - Parameters:
    ///   - windowScene: The window scene to present the review prompt.
    ///   - conditionAfterWait: The condition which is asked after some wait time.
    func requestReview(in windowScene: UIWindowScene, conditionAfterWait condition: @escaping () -> Bool) {

        // Cancel previous request.
        requestReviewWorkItem?.cancel()

        // Make new request work.
        requestReviewWorkItem = DispatchWorkItem(block: { [weak self] in
            if condition() {
                SKStoreReviewController.requestReview(in: windowScene)
                self?.lastVersionPromptedForReview = self?.currentAppVersion
            }
        })

        // Scedule the request.
        DispatchQueue.main.asyncAfter(deadline: .now() + waitTimeForReviewRequest, execute: requestReviewWorkItem!)
    }

}