The use of Swift 3 objc inference in Swift 4 mode is deprecated

Question

Briefly  while using Xcode 9 Beta  I have run into the following warning      The use of Swift 3  objc inference in Swift 4 mode is deprecated  Please address deprecated  objc inference warnings  test your code with    Use of deprecated Swift 3  objc inference    logging enabled  and disable Swift 3  objc inference      After some research  I still have no idea how to fix the issue   I would greatly appreciate any tips on how to fix this issue as well as an explanation of what is going on    My goal is to grasp a better understanding of what is happening with my code

User · Answer

You can try to  Pod update  and or  flutter clean   I also set this setting in xcode   The Objective-C interface setting is as follows

User · Answer

- What is  objc inference  What is going on   In Swift 3  the compiler infers  objc in a number of places so you wouldn t have to  In other words  it makes sure to add  objc for you   In Swift 4  the compiler no longer does this  as much   You now must add  objc explicitly   By default  if you have a pre-Swift 4 project  you will get warnings about this  In a Swift 4 project  you will get build errors  This is controlled via the SWIFT SWIFT3 OBJC INFERENCE build setting  In a pre-Swift 4 project this is set to On  I would recommend to set this to Default  or Off   which is now the default option on a new project    It will take some time to convert everything  but since it s the default for Swift 4  it s worth doing it   - How do I stop the compiler warnings errors   There are two ways to go about converting your code so the compiler doesn t complain   One is to use  objc on each function or variable that needs to be exposed to the Objective-C runtime    objc func foo          The other is to use  objcMembers by a Class declaration  This makes sure to automatically add  objc to ALL the functions and variables in the class  This is the easy way  but it has a cost  for example  it can increase the size of your application by exposing functions that did not need to be exposed    objcMembers class Test          - What is  objc and why is it necessary   If you introduce new methods or variables to a Swift class  marking them as  objc exposes them to the Objective-C runtime  This is necessary when you have Objective-C code that uses your Swift class  or  if you are using Objective-C-type features like Selectors  For example  the target-action pattern  button addTarget self  action  selector didPressButton   for  touchUpInside   - Why would I not mark everything  objc   There are negatives that come with marking something as  objc    Increased application binary size  No function overloading     Please keep in mind that this is a very high-level summary and that it is more complicated than I wrote  I would recommend reading the actual proposal for more information   Sources    https   github com apple swift-evolution blob master proposals 0160-objc-inference md https   developer apple com library content documentation Swift Conceptual BuildingCocoaApps WritingSwiftClassesWithObjective-CBehavior html   apple ref doc uid TP40014216-CH5-ID86

User · Answer

The use of Swift 3  objc inference in Swift 4 mode is deprecated    use func call  objc   func call     foo        objc func foo

User · Answer

You can simply pass to  default  instead of  ON   Seems more adherent to Apple logic    but all the other comments about the use of  obj remains valid

User · Answer

All you need just run a test wait till finish  after that go to  Build Setting   Search in to Build Setting Inference  change swift 3  objc Inference to  Default   that s all what i did and worked perfect

User · Answer

I had this warning with  Swift 3  objc Inference     Default  setting  Then I realized that is was set for the Project - not for the target  So  make sure that you have  Default  setting in your target to get rid of the warning

User · Answer

Migrator cannot identify all the functions that need  objc Inferred Objective-C thunks marked as deprecated to help you find them     Build warnings about deprecated methods     Console messages when running deprecated thunks

User · Answer

On top of what  wisekiddo said  you can also modify your build settings in the project pbxproj file by setting the Swift 3  obj Inference to default like SWIFT SWIFT3 OBJC INFERENCE   Default  for your build flavors  i e  debug and release   especially if you re coming from some other environment besides Xcode

User · Answer

I got rid of this warning by changing the  quot Swift 3  objc Inference quot  build setting of my targets to  quot Default quot    From this article   Before Swift 4  the compiler made some Swift declarations automatically available to Objective-C  For example  if one subclassed from NSObject  the compiler created Objective-C entry points for all methods in such classes  The mechanism is called  objc inference  In Swift 4  such automatic  objc inference is deprecated because it is costly to generate all those Objective-C entry points  When  quot Swift 3  objc Inference quot  setting is set to  quot On quot   it allows the old code to work  However  it will show deprecation warnings that need to be addressed  It is recommended to  quot fix quot  these warnings and switch the setting to  quot Default quot   which is the default for new Swift projects   Please also refer to this Swift proposal for more information

User · Answer

I m an occasional iOS dev  soon to be more  but I still couldn t find the setting as guided by the other answer  since I did not have that Keychain item the answer shows   so now that I found it I thought I might just add this snapshot with the highlighted locations that you will need to click and find    Start in the upper left Choose the project folder icon Choose your main project name below the project folder icon  Choose Build Settings on the right side  Choose your project under TARGETS  Scroll very far down  or search for the word inference in search text box

User · Answer

Swift 3  objc Inference The use of Swift 3  objc inference in Swift 4 mode is deprecated  Please address deprecated  objc inference warnings  test your code with    Use of deprecated Swift 3  objc inference    logging enabled  and then disable inference by changing the  Swift 3  objc Inference  build setting to  Default  for the  XMLParsingURL  target   got to the    First step got Build Setting Search in to Build Setting Inference change swift 3  objc Inference Default   enter image description here

User · Answer

Indeed  you ll get rid of those warnings by disabling Swift 3  objc Inference  However  subtle issues may pop up  For example  KVO will stop working  This code worked perfectly under Swift 3   for  key  value  in jsonDict       if self value forKey  key     nil           self setValue value  forKey  key            After migrating to Swift 4  and setting  Swift 3  objc Inference  to default  certain features of my project stopped working  It took me some debugging and research to find a solution for this  According to my best knowledge  here are the options    Enable  Swift 3  objc Inference   only works if you migrated an existing project from Swift 3   Mark the affected methods and properties as  objc  Re-enable ObjC inference for the entire class using  objcMembers    Re-enabling  objc inference leaves you with the warnings  but it s the quickest solution  Note that it s only available for projects migrated from an earlier Swift version  The other two options are more tedious and require some code-digging and extensive testing   See also https   github com apple swift-evolution blob master proposals 0160-objc-inference md

[swift] The use of Swift 3 @objc inference in Swift 4 mode is deprecated?

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