KTLN-654 Code update based on received article comment.

Author: zeesh49

kotlin-patterns/src/main/kotlin/com/baeldung/railwayorientedprogramming/ROP.kt

@@ -4,26 +4,35 @@ data class Customer(val name: String, val emailAddress: String)
 
 object ROP {
     fun createAndSave(args: Array<String>): Result<String> {
-        return validateName(args.toList()) then ::validateEmail then ::createCustomerDAO then ::save
+        return Success(args.toList()) then ::parse then ::validateCustomerName then ::validateCustomerEmail then ::saveCustomer otherwise ::error
     }
 
-    fun validateName(inp: List<String>): Result<List<String>> {
-        if(inp.get(0).length < 10) {
-            return Failure("Name validation failed. Name must be greater than 10 characters.")
-        }else{
-            return Success(inp)
+    private fun parse(inp: List<String>): Result<Customer> {
+        return Success(Customer(inp.get(0), inp.get(1)))
+    }
+
+    private fun validateCustomerName(customer: Customer): Result<Customer> {
+        if (customer.name.length < 10) {
+            return Failure("Name validation failed; name length must be greater than 10 characters")
+        } else {
+            return Success(customer)
         }
     }
 
-    fun validateEmail(inp: List<String>): Result<List<String>> {
-        if(inp.get(1).contains("@")) {
-            return Success(inp)
-        }else{
-            return Failure("Email validation failed. Email must contain '@' symbol.")
+    private fun validateCustomerEmail(customer: Customer): Result<Customer> {
+        if (customer.emailAddress.contains("@")) {
+            return Success(customer)
+        } else {
+            return Failure("Email validation failed; email must contain the '@' symbol")
         }
     }
 
-    fun createCustomerDAO(inp: List<String>): Result<Customer> = Success(Customer(inp.get(0), inp.get(1)))
+    private fun saveCustomer(customer: Customer): Result<String> {
+        return Success("Customer successfully saved: " + customer)
+    }
+
+    private fun error(message: String): Failure<String> {
+        return Failure("Error: ${message}")
+    }
 
-    fun save(customer: Customer): Result<String> { return Success("Customer successfully saved: " + customer) }
 }

kotlin-patterns/src/main/kotlin/com/baeldung/railwayorientedprogramming/Result.kt

@@ -1,13 +1,17 @@
 package com.baeldung.railwayorientedprogramming
 
 sealed class Result<T>
-data class Success<T>(val value: T): Result<T>()
-data class Failure<T>(val errorMessage: String): Result<T>()
-infix fun <T,U> Result<T>.then(f: (T) -> Result<U>) =
+data class Success<T>(val value: T) : Result<T>()
+data class Failure<T>(val errorMessage: String) : Result<T>()
+
+infix fun <T, U> Result<T>.then(f: (T) -> Result<U>) =
     when (this) {
         is Success -> f(this.value)
         is Failure -> Failure(this.errorMessage)
     }
 
-infix fun <T> Result<T>.otherwise(f: (String) -> Unit) =
-    if (this is Failure) f(this.errorMessage) else Unit
+infix fun <T> Result<T>.otherwise(f: (String) -> Failure<T>) =
+    when (this) {
+        is Success -> Success(this.value)
+        is Failure -> f(this.errorMessage)
+    }

kotlin-patterns/src/test/java/com/baeldung/railwayorientedprogramming/ROPUnitTest.kt

@@ -6,32 +6,48 @@ import org.junit.jupiter.api.Test
 class ROPUnitTest {
     @Test
     fun `create and save customer successfully`() {;
-        val customer = Customer("Zeeshan Arif Saeed"
-            , "[email protected]")
-        val res = ROP.createAndSave(arrayOf("Zeeshan Arif Saeed"
-            , "[email protected]"))
-        assertInstanceOf(res::class.java,
-            Success("Customer successfully saved: " + customer))
+        val customer = Customer(
+            "Zeeshan Arif Saeed", "[email protected]"
+        )
+        val res = ROP.createAndSave(
+            arrayOf(
+                "Zeeshan Arif Saeed", "[email protected]"
+            )
+        )
+        assertInstanceOf(
+            res::class.java,
+            Success("Customer successfully saved: " + customer)
+        )
     }
 
     @Test
     fun `create and save customer name validatation failure`() {;
-        val customer = Customer("Zeeshan"
-            , "[email protected]")
-        val res = ROP.createAndSave(arrayOf("Zeeshan"
-            , "[email protected]"))
-        assertInstanceOf(res::class.java,
+        val customer = Customer(
+            "Zeeshan", "[email protected]"
+        )
+        val res = ROP.createAndSave(
+            arrayOf(
+                "Zeeshan", "[email protected]"
+            )
+        )
+        assertInstanceOf(
+            res::class.java,
             Failure<String>("Name validation failed. Name must be greater than 10 characters.")
         )
     }
 
     @Test
     fun `create and save customer email validatation failure`() {;
-        val customer = Customer("Zeeshan Arif Saeed"
-            , "[email protected]")
-        val res = ROP.createAndSave(arrayOf("Zeeshan"
-            , "[email protected]"))
-        assertInstanceOf(res::class.java,
+        val customer = Customer(
+            "Zeeshan Arif Saeed", "[email protected]"
+        )
+        val res = ROP.createAndSave(
+            arrayOf(
+                "Zeeshan", "zeesh.arifgmail.com"
+            )
+        )
+        assertInstanceOf(
+            res::class.java,
             Failure<String>("Email validation failed. Email must contain '@' symbol.")
         )
     }