iOS SDK API for NSLocale makes old properties inaccessible to iOS 8 & 9

Originator:christian.tietze
Number:rdar://28363526 Date Originated:2016-09-19
Status:Closed Resolved:
Product:iOS SDK Product Version:
Classification:Serious Bug Reproducible:Always
 
Summary:
The compiler (tested with Swift 2.3) complains about using NSLocale properties when deploying to iOS 8/9 even though the same property names were available before.

Steps to Reproduce:

// Create target to deploy to iOS 8.x or 9.x
import Foundation
// here the compiler will complain:
let symbol = NSLocale.autoupdatingCurrentLocale().currencySymbol

Expected Results:
Upgrading to Swift 2.3 would continue to work. Maybe a few adjustments here and there.

Actual Results:
The compiler informs me that currencyCode and others are marked as available for iOS 10+ only and that my code has to take this into account. 

The thing is: since this is a runtime switch and not a compile time switch, I cannot compile with the new SDK for the old version; I have to provide an alternative code path for devices running iOS 8/9. But the only alternative is to use the property with the same name. Only the compiler won't allow.


Version:
iOS 8.1

Notes:


Configuration:
Xcode 8.0

Attachments:

Comments

Response by Apple

Engineering has determined that this issue behaves as intended based on the following information:

These properties are new in iOS 10, and you could add equivalent properties for older OSes using an extension like the one shown below:

currencyCode was an API that was added in iOS 10; it cannot be back-deployed safely since it did not exist before iOS 10.

It is effectively a wrapper around -[NSLocale objectForKey:NSLocaleCurrencySymbol] which returns a type safe return value.

So, you could have an extension of:

extension NSLocale { var compatabilityCurrencySymbol: String? { return objectForKey(NSLocaleCurrencySymbol) as? String } }

By christian.tietze at Sept. 27, 2016, 7:58 a.m. (reply...)

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