Swift

iOS Notification Actions Explained for Interview Custom notification actions let users interact with a notification without opening the app. When the user long-presses a notification, buttons like Reply, Like, or Track Order appear inline — powered by UNNotificationAction and UNNotificationCategory. The Mental Model Before writing any code, it helps to understand the three-layer architecture: 1 2 3 UNNotificationAction → a single button UNNotificationCategory → a named group of those buttons APNs payload "category" → tells iOS which group to render The category string in your APNs payload is the linking pin between what your backend sends and what iOS renders. Get that string wrong and no buttons appear — with no error thrown. ...

Local Notifications and Geofencing in iOS Most iOS developers encounter push notifications first — the server-side setup, APNs configuration, device tokens. It’s the more visible part of the notifications system. But there’s an entire category of notifications that require none of that infrastructure: no server, no APNs, no internet connection. Just your app, iOS, and a trigger condition. Local notifications are scheduled entirely on-device. From the user’s perspective, they’re identical to a push notification — same banner, same lock screen card, same sound. But the entire lifecycle happens locally. The user can be on a plane in airplane mode and your notification fires exactly when it should. ...

Push Notifications in iOS: A Complete Guide Push notifications are one of those iOS features that look straightforward from the outside — a banner appears, the user taps it, something happens. But once you start building a production system around them, you realise there are a surprising number of moving parts: APNs environments, device token lifecycle, background execution budgets, notification categories, the delegate method that handles three different app states. Get any one of these wrong and notifications silently stop working with no error thrown anywhere. ...

There’s a question I ask every iOS candidate I interview: “Walk me through what happens from the moment a user taps your app icon to the moment they’re looking at your home screen.” Most developers answer this with a list of method names. Senior developers answer it with a mental model. Staff engineers answer it by asking a clarifying question first — “Are we talking UIKit or SwiftUI? What iOS deployment target?” — because the answer genuinely differs, and knowing when it differs is the whole point. ...