Alerts

Alerts manages displaying UIAlertControllers in succession by coordinating them in a queue.

Motivation

The main reason of creating this project was provide a fix for the following console log:

Warning: Attempt to present UIAlertController: on viewController: which is already presenting

when presenting multiple alerts. If are aware of this message then you understand the use case of coordinating alerts in your app. Especially in apps that heavily rely on alerts.

Requirements

Swift 5.0+ Xcode 14 iOS 11.0+

Demo

How

The project is built on three objects: Alert, AlertAction and AlertCoordinator.

AlertCoordinator

Alerts are managed by an AlertCoordinator singleton (AlertCoordinator.main) which holds three queues based on priority. The queues follow a First In First Out (FIFO) sequence. The coordinator queues up alerts based on priority automatically, can be paused, and told when to display alerts. The coordinator manages three queues internally for high, default and low alerts. The higher priority alerts are dequeued first followed by default then low.

Alert

Alert is a wrapper class on UIAlertController that adds functionality for priority. Apple strictly states to not subclass UIAlertController for adding features so the class only holds a UIAlertController class within and doesn't subclass it.

Alert Priority

An Alert class holds a priority for the coordinator to queue the alert correctly.

High

Higher priority alerts are presented first and can also present over lower priority alerts when added to the coordinator if it is actively displaying. If a high priority alert is on display already and another high is added then the waits for the current to be dismissed.

Medium

Medium priority is the default priority and acts like a normal alert. If a higher is priority is added the coordinator will dismiss a default priorty alert and it will be queued up again to be displayed after the higher queue is completed.

Low

Low priority is for alerts that don't need much action and will be dismissed and discarded if another higher priority alert is queued.

AlertAction

AlertAction is a wrapper class on UIAlertAction that are actions for an Alert. The AlertAction will notify the AlertCoordinator on completion automatically to allow other others to display. Long running actions can be performed on an AlertAction that can keep other alerts from displaying until the task is complete. When the task is complete manually call the complete() class method to notify the coordinator on the task completion.

Code Example

Simple alert

let helloWorldAlert = Alert(title: "Hello", message: "World", alertActions: [.defaultAction()]) // .defaultAction() creates a default confirmation AlertAction with a title of Okay
AlertCoordinator.main.enqueue(alert: helloWorldAlert)
AlertCoordinator.main.display()

Multiple Alerts

for i in 0...5 {
    let alert = Alert(title: "\(i)", message: "", alertActions: [.defaultAction()])    
    AlertCoordinator.main.enqueue(alert: alert)
}
AlertCoordinator.main.display() // Alerts from 0 to 5 display in order

Long running tasks Alert

If you want to display an alert and hold the coordinator from displaying any other alerts until a task is completed.

let paymentAction = AlertAction(title: "Yes", style: .default, preferred: true, completeOnDismiss: false) { alert in
    // present another view controller for payment and on it's dismissal call AlertAction.complete()
    self.present(paymentVC, animated: true, completion: nil)
}

let alert = Alert(title: "Make a payment", message: "No", alertActions: [.defaultAction()])
alert.actions = [.defaultAction(), paymentAction]
AlertCoordinator.main.enqueue(alert: alert)
AlertCoordinator.main.display()


/// In PaymentViewController.swift
/// completes payment
func completePayment {
    dismiss(animated: true) {
        AlertAction.complete() // Alert Coordinator will begin to display any pending alerts in queue
    }
}

Priority Alerts

let high = Alert(title: "High", message: "Message", priority: .high, alertActions: nil)
let medium = Alert(title: "Default", message: "Message", priority: .medium, alertActions: nil)
let low = Alert(title: "Low", message: "Message", priority: .low, alertActions: nil)

Installation

Manually

Copy over the AlertCoordinator.swift file from the Alert folder in the project to your project.

Contributors

Joshua Alvarado - Twitter

License

This project is released under the MIT license.