Objective C & Swift & iOS & App
https://www.runoob.com/ios/ios-objective-c.html
https://www.runoob.com/swift/swift-tutorial.html
https://www.runoob.com/manual/gitbook/swift3/source/_book/chapter2/01_The_Basics.html
swift 5
https://docs.swift.org/swift-book/GuidedTour/GuidedTour.html
https://swift.org/blog/swift-5-released/
http://www.cocoachina.com/ios/20180518/23420.html
xgqfrms 2012-2020
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