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State management using Kotlin's Sealed Classes Harun Wangereka Android Developer @ Apps:Lab

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? ? ? ? ? ?

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sealed class Result { data class Success(val data: List) : Result() data class Failure(val exception: Throwable) : Result() }

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sealed class Result { data class Success(val data: List) : Result() data class Failure(val exception: Throwable) : Result() } `else` clause not required, all the cases covered

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Register User Enter Details

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fun registerUser(fullName : String , email :String,password : String){ // TODO Make a register request // TODO Parse register response // TODO Save created user data // TODO proceed to dashboard screen }

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fun registerUser(fullName : String , email :String,password : String){ val response = registerRequest(fullName, email, password) if (response.isSuccessful){ saveUserDetails(response.body()) proceedToDashBoard() } }

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fun registerUser(fullName : String , email :String,password : String){ val response = registerRequest(fullName, email, password) if (response!!.isSuccessful){ saveUserDetails(response.body()) proceedToDashBoard() }else{ showError("An error occurred") } }

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fun registerUser(fullName : String , email :String,password : String){ try { val response = registerRequest(fullName, email, password) if (response!!.isSuccessful){ saveUserDetails(response.body()) proceedToDashBoard() }else{ showError("An error occurred") } }catch (error : IOException){ Log.d("Error",error.message) } }

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else{ showError("An error occurred") } } Catch more errors!

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when(response.code()){ 401 -> showError("Unauthorized") 403 -> showError("Access to resource is forbidden") 404 -> showError("Resource not found") 500 -> showError("Internal Server error") 502 -> showError("Bad Gateway") 301 -> showError("Resource has been removed permanently") 302 -> showError("Resource moved,but has has been found ") else -> showError("All cases have not been covered!!") }

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!!

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if (response.isSuccessful){ if(response != null){ saveUserDetails(response.body()) proceedToDashBoard() }else{ showError("Response is null") } }

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Another sealed class Also has state sealed class RegisterResult { data class Success(val data : String) : RegisterResult() object InvalidData :RegisterResult() data class Error(val error : String) : RegisterResult() data class NetworkException(val error : String) : RegisterResult() sealed class HttpErrors : RegisterResult() { }

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sealed class HttpErrors : RegisterResult() { data class Unauthorized(val exception: String) : HttpErrors() data class ResourceForbidden(val exception: String) : HttpErrors() data class ResourceNotFound(val exception: String) :HttpErrors() data class InternalServerError(val exception: String) :HttpErrors() data class BadGateWay(val exception: String) : HttpErrors() data class ResourceRemoved(val exception: String) : HttpErrors() data class RemovedResourceFound(val exception: String) :HttpErrors() }

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fun registerUser(fullName : String , email :String,password : String) : RegisterResult{ return try { val response = registerRequest(fullName, email, password) if (response.isSuccessful) { if (response != null) { RegisterResult.Success(response.body()!!) }else{ RegisterResult.InvalidData } }else{ when(response.code()){ 401 -> RegisterResult.HttpErrors.Unauthorized(response.message()) 403 -> RegisterResult.HttpErrors.ResourceForbidden(response.message()) 404 -> RegisterResult.HttpErrors.ResourceNotFound(response.message()) 500 -> RegisterResult.HttpErrors.InternalServerError(response.message()) 502 -> RegisterResult.HttpErrors.BadGateWay(response.message()) 301 -> RegisterResult.HttpErrors.ResourceRemoved(response.message()) 302 -> RegisterResult.HttpErrors.RemovedResourceFound(response.message()) else -> RegisterResult.Error(response.message()) } } }catch (error : Exception){ RegisterResult.NetworkException(error.message) } }

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private fun handleRegisterResult(result: RegisterResult){ when(result){ is RegisterResult.Success -> { saveUserDetails(result.data) proceedToDashBoard() } is RegisterResult.HttpErrors.Unauthorized -> showError(result.exception) is RegisterResult.HttpErrors.ResourceForbidden -> showError(result.exception) is RegisterResult.HttpErrors.ResourceNotFound -> showError(result.exception) is RegisterResult.HttpErrors.InternalServerError -> showError(result.exception) is RegisterResult.HttpErrors.BadGateWay -> showError(result.exception) is RegisterResult.HttpErrors.RemovedResourceFound -> showError(result.exception) is RegisterResult.NetworkException -> showError(result.error) is RegisterResult.Error -> showError(result.error) } }

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Thank You! Harun Wangereka Android Developer @ Apps:Lab @wangerekaharun