Important topics for iOS developers

Delegates
CoreData
SplitViewController
UIPageViewController

https://www.appcoda.com/ios-programming-course/
GitHub
map, filter, reduce, flatMap and compactMap, guard, if Let or if Var, do, try-catch, Any, AnyObject and AnyHashable
Cloud Kit
Drop Box, DropBox integration
Debuging, unit testing, XI/UITesting, Instruments
Class & Struct
JSON parsing with Structs example
SnapKit for constraints
Safe area layout for iPhoneX
AV Kit
TV OS

Custom URL to open iOS app
UIBezierPath
CAShapeLayer
Chating based apps
uidocumentinteractioncontroller
Read bar codes
Payment Gateways
Jazzy
SQLITE
Top 10 Libraries for iOS Developers
Realm
Apple history year wise
Importent concepts in swift
http://brainwashinc.com/2009/05/
http://www.theappguruz.com/category/ios
RxSwift
SandBox testing
Firebase push notifications with badge, sound and Custom designed notifications
Autolayout programmetically
MKMapKit, Apple maps
Ad mobs , and google ad mobs
iAd Banner
XML Parsing
Xib examples with constraints
Work with php, .net and java API’s
Create developer, Production and Distribution Certificates
Push notifications Badge

https://www.programiz.com/swift-programming/sets
Firebase Database
Integrate files
Perform background tasks
Relations Coredata
Threading tutorial
Swift patterns
HealthKit
Appcoda tutorial links
Best Tutorial for File management and Dropbox integration and so on …
Firebase cloud storage ( Cloud Firestore)
Best Tutorials
Push notifications tutorial
UICollectionViewCells Grid/HeaderAndFooter/Multiple selection
UICollectioViewFlowLayout
Local notifications
SQLite tutorial
KYO & KYC
Apple Push Notification service (APNS)
MVC & MVVC
How to open Deep Links, Notifications and Shortcuts
Custom font import