Shift

Light-weight EventKit wrapper.

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Shift is a light-weight concurrency wrapper for EventKit:

• Concurrency ready with async/await. (tag: 0.7.0)
• Tranditional, Result completion handler if preferred (tag: 0.6.0)
• Thread-safe.
• SwiftUI supported.

Shift is currently being used by Clendar app.

Requirement

• iOS 15.0 for async/await, tag 0.7.0
• iOS 14.0 and below for Result-based, tag <0.6.0
• Swift version 5.5
• Xcode 13.1

Install

This component is built using Swift Package Manager, it is pretty straight forward to use:

1. In Xcode (11+), open your project and navigate to File > Swift Packages > Add Package Dependency...
2. Paste the repository URL (https://github.com/vinhnx/Shift) and click Next.
3. For Rules, select Version, in here, you can choose either:

• Async/await => tag 0.7.0
• Result-based completion handler => tag 0.6.0

5. Click Finish to resolve package into your Xcode project.

Tag Version:

Concurrency support is now ready, in tag 0.7.0

In order to use old Result-based completion hanlders, please use tag 0.6.0.

Getting Started

First thing first:

• Add Calendar usage description to your app's Info.plist to request for user's Calendars access.

<key>NSCalendarsUsageDescription</key>
<string>&quot;$(PRODUCT_NAME) needs your permission to create events&quot;</string>

• (Optional) configure own calendar name to request access to, preferrable in AppDelegate's didFinishLaunchingWithOptions (Swift) or App's init() (SwiftUI):

Swift AppDelegate:

import UIKit
@UIApplicationMainclassAppDelegate:UIResponder,UIApplicationDelegate{func application(_ application:UIApplication, didFinishLaunchingWithOptions launchOptions:[UIApplication.LaunchOptionsKey:Any]?)->Bool{
// Override point for customization after application launch.
Shift.configureWithAppName("MyApp")returntrue}}

in SwiftUI App, first import Shift, then configure your app's name to differntiate the name of your app's calendar in system's EventKit.

import SwiftUI
import Shift
@mainstructMyApp:App{init(){Shift.configureWithAppName("MyApp")}varbody:someScene{WindowGroup{ContentView()}}}

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A quick NOTE about concurrency

Since async functions can only be called on concurrency context, if you call async function inside synchornouse context, Xcode will throws an error:

So, there are two ways to awaiting for concurrency result, base on context:

• Inside async function

func doSomethingAsync()async{
// ... other works
letevents=try?awaitShift.shared.fetchEvents(for:Date())
// ... other works
}

• Inside Task closure:

func regularFunction(){
// ... other works
Task{letevents=try?awaitShift.shared.fetchEvents(for:Date())
// then...
}
// ... other works
}

Either is fine, base on caller's context.

You can read more about Task here https://developer.apple.com/documentation/swift/task.

In SwiftUI views, you can call async functions inside View' .task modifier:

import EventKit
import SwiftUI
import Shift
structContentView:View{@StateObjectvareventKitWrapper=Shift.shared
@StateprivatevarselectedEvent:EKEvent?varbody:someView{LazyVStack(alignment:.leading, spacing:10){ForEach(eventKitWrapper.events, id: \.self){ event inText(event: event)}}.padding().task{ // wrap async call inside .task modifier
try?await eventKitWrapper.fetchEventsForToday()}}}

You can read more about SwiftUI's .task modifier here https://developer.apple.com/documentation/swiftui/view/task(priority:_:).

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Usage Example

Fetch list of events for a particular date:

async/await (NEW)

inside regular async function:

func fetchEvents()async{do{letevents=tryawaitShift.shared.fetchEvents(for:Date()) // await for events fetching
}catch{print(error) // handle error
}}

or standalone:

Task{letevents=try?awaitShift.shared.fetchEvents(for:Date()) // await for events fetching
}

Result-based completion handlers (old pattern, but still doable if you preferred this to async/await)

Shift.shared.fetchEvents(for:Date()){ result inswitch result {caselet.success(events):print(events) // got events
caselet.failure(error):print(error) // handle error
}}

Shift.shared.fetchEventsRangeUntilEndOfDay(from:Date()){ result inswitch result {caselet.success(events):print(events) // got events
caselet.failure(error):print(error) // handle error
}}

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Create Event:

async/await

inside regular async function:

func myAsyncFunction()async{try?awaitShift.shared.createEvent("Be happy!", startDate: startTime, endDate: endTime)}

or standalone:

Task{try?awaitShift.shared.createEvent("Be happy!", startDate: startTime, endDate: endTime)}

Result

Shift.shared.createEvent("Be happy!", startDate: startTime, endDate: endTime){ result inswitch result {caselet.success(event):print(event) // created event
caselet.failure(error):print(error) // handle error
}}

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Delete event:

async/await

inside regular async function:

func myAsyncFunction()async{try?awaitShift.shared.deleteEvent(identifier: eventID)}

or standalone:

Task{try?awaitShift.shared.deleteEvent(identifier: eventID)}

Result

Shift.shared.deleteEvent(identifier: eventID){ result inswitch result {caselet.success:print("done!") // deleted event
caselet.failure(error):print(error) // handle error
}}

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SwiftUI Example

Shift is conformed ObservableObject with an @Publishedevents property, so it's straight-forward to use in SwiftUI binding mechanism.

Result-based example:

import EventKit
import SwiftUI
import Shift
structContentView:View{@StateObjectvareventKitWrapper=Shift.shared
@StateprivatevarselectedEvent:EKEvent?varbody:someView{LazyVStack(alignment:.leading, spacing:10){ForEach(eventKitWrapper.events, id: \.self){ event inText(event: event)}}.padding().onAppear{
eventKitWrapper.fetchEventsForToday()}}}

async/await example:

import EventKit
import SwiftUI
import Shift
structContentView:View{@StateObjectvareventKitWrapper=Shift.shared
@StateprivatevarselectedEvent:EKEvent?varbody:someView{LazyVStack(alignment:.leading, spacing:10){ForEach(eventKitWrapper.events, id: \.self){ event inText(event: event)}}.padding().task{try?await eventKitWrapper.fetchEventsForToday()}}}

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Apps currently using Shift

• Clendar - Clendar - universal calendar app. Written in SwiftUI. Available on App Store. MIT License.

(add yours here)

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Help, feedback or suggestions?

Feel free to open an issue or contact me on Twitter for discussions, news & announcements & other projects. 🚀

I hope you like it! :)