```isMainThread true Function doesn t have or inherit Throws

Question

```isMainThread true Function doesn t have or inherit Throws annotation and thus exception isn t propagated from Kotlin to Objective C Swift as NSError It is considered unexpected and unhandled instead Program will be terminated Uncaught Kotlin exception kotlin native concurrent InvalidMutabilityException mutation attempt of frozen com berlin kmm demo shared ApiService 2a37878 at 0 shared 0x0000000100c192dd kfun kotlin Throwable lt init gt kotlin String + 93 Users teamcity buildAgent work cae0e6559deed4c4 runtime src main kotlin kotlin Throwable kt 23 37 at 1 shared 0x0000000100c121cb kfun kotlin Exception lt init gt kotlin String + 91 Users teamcity buildAgent work cae0e6559deed4c4 runtime src main kotlin kotlin Exceptions kt 23 44 at 2 shared 0x0000000100c1238b kfun kotlin RuntimeException lt init gt kotlin String + 91 Users teamcity buildAgent work cae0e6559deed4c4 runtime src main kotlin kotlin Exceptions kt 34 44 at 3 shared 0x0000000100c4793b kfun kotlin native concurrent InvalidMutabilityException lt init gt kotlin String + 91 Users teamcity buildAgent work cae0e6559deed4c4 runtime src main kotlin kotlin native concurrent Freezing kt 22 60 at 4 shared 0x0000000100c491f2 ThrowInvalidMutabilityException + 690 Users teamcity buildAgent work cae0e6559deed4c4 runtime src main kotlin kotlin native concurrent Internal kt 92 11 at 5 shared 0x0000000100d4136c MutationCheck + 108 at 6 shared 0x0000000100bb7ce7 kfun com berlin kmm demo shared ApiService lt init gt + 455 at 7 shared 0x0000000100bbc743 objc2kotlin + 163 at 8 iosApp 0x0000000100ae655f $sSo16SharedApiServiceCABycfC + 31 at 9 iosApp 0x0000000100ae6467 $s6iosApp12getLocationsyyF + 39 Users skhawase skunkworks KMM Demo iosApp iosApp ContentView swift 13 1 at 10 iosApp 0x0000000100ae6eaa $s6iosApp11ContentViewV4bodyQrvgyycfU + 442 Users skhawase skunkworks KMM Demo iosApp iosApp ContentView swift 20 9 at 11 SwiftUI 0x00007fff55f13d0c $sIeg ytIegr TR + 12 at 12 SwiftUI 0x00007fff55e22b01 $sIeg ytIegr TRTA + 17 at 13 SwiftUI 0x00007fff55f13d2c $sytIegr Ieg TR + 12 at 14 SwiftUI 0x00007fff55f13d0c $sIeg ytIegr TR + 12 at 15 SwiftUI 0x00007fff55e22b01 $sIeg ytIegr TRTA + 17 at 16 SwiftUI 0x00007fff55e22c09 $sIeg ytIegr TRTA 8 + 9 at 17 SwiftUI 0x00007fff5636e239 $s7SwiftUI16ViewRendererHostPAAE6render8interval17updateDisplayListySd SbtFyyXEfU + 1657 at 18 SwiftUI 0x00007fff5636d2f7 $s7SwiftUI16ViewRendererHostPAAE6render8interval17updateDisplayListySd SbtF + 343 at 19 SwiftUI 0x00007fff564d4e41 $s7SwiftUI14 UIHostingViewC14layoutSubviewsyyF + 241 at 20 SwiftUI 0x00007fff564d4e65 $s7SwiftUI14 UIHostingViewC14layoutSubviewsyyFTo + 21 at 21 UIKitCore 0x00007fff24bcd686 UIView CALayerDelegate layoutSublayersOfLayer + 2874 at 22 QuartzCore 0x00007fff27a5ae67 CALayer layoutSublayers + 258 at 23 QuartzCore 0x00007fff27a61319 ZN2CA5Layer16layout if neededEPNS 11TransactionE + 575 at 24 QuartzCore 0x00007fff27a6d071 ZN2CA5Layer28layout and display if neededEPNS 11TransactionE + 65 at 25 QuartzCore 0x00007fff279ad158 ZN2CA7Context18commit transactionEPNS 11TransactionEdPd + 496 at 26 QuartzCore 0x00007fff279e3ef3 ZN2CA11Transaction6commitEv + 783 at 27 UIKitCore 0x00007fff2468ab96 34 UIApplication firstCommitBlock block invoke 2 + 81 at 28 CoreFoundation 0x00007fff203a85db CFRUNLOOP IS CALLING OUT TO A BLOCK + 12 at 29 CoreFoundation 0x00007fff203a79ef CFRunLoopDoBlocks + 434 Process finished with exit code 0```

Maurice Jouvet · Answer

Hey what is the method that you call from iOS Just the header of the method

BollywoodVillain · Answer

I fixed the issue by moving the Json formatter inside the `KotlinXSerializer` init You can find the final working source code here <https github com samkhawase Kotlin MPP Demo>