Simple Number Validator

Part of the Logic & Flow section of Coddy's GO journey — lesson 67 of 68.

Challenge

Easy

Create a number validation system that demonstrates how interfaces define behavior contracts while custom errors provide meaningful feedback when validation fails. This challenge will test your ability to create interfaces, implement them with custom types, and handle validation errors appropriately.

You will receive two inputs:

A string containing numbers to validate separated by commas (e.g., "45,150,25,200,75")
A string containing the validation range in the format "min:max" (e.g., "1:100")

Your task is to:

Define a Validator interface with a single method: Validate() error
Create a custom error type called ValidationError struct with two fields: Value (int) and Message (string)
Implement the Error() string method for ValidationError that returns the message in the format: "Validation failed: [message] (value: [value])"
Create a NumberValidator struct with three fields: Number (int), Min (int), and Max (int)
Implement the Validate() error method for NumberValidator that:
- Returns nil if the number is within the valid range (inclusive)
- Returns a ValidationError with message "number below minimum range" if the number is less than the minimum
- Returns a ValidationError with message "number above maximum range" if the number is greater than the maximum
Parse the first input by splitting on commas to get individual number strings
Parse the second input by splitting on colons to extract minimum and maximum values
Convert all string values to integers using the strconv package
Display the validation header: "=== NUMBER VALIDATION SYSTEM ==="
Display the validation parameters: "Validating numbers in range [min] to [max]"
For each number:
- Create a NumberValidator instance with the number and range values
- Call the Validate() method on the validator
- If validation passes (error is nil), display: "✓ [number] is valid"
- If validation fails (error is not nil), display: "✗ [error_message]"
Display validation summary:
- "=== VALIDATION SUMMARY ==="
- "Total numbers checked: [total_count]"
- "Valid numbers: [valid_count]"
- "Invalid numbers: [invalid_count]"
Display the completion message: "Number validation completed successfully"

Use the strings package to split input strings, the strconv package to convert strings to integers, and the fmt package for formatted output. This challenge demonstrates how to create flexible validation systems using interfaces while providing detailed error information through custom error types.

Try it yourself

package main

import (
	"fmt"
	"strconv"
	"strings"
)

func main() {
	// Read input
	var numbersInput string
	var rangeInput string
	fmt.Scanln(&numbersInput)
	fmt.Scanln(&rangeInput)
	
	// Parse the inputs
	numberStrings := strings.Split(numbersInput, ",")
	rangeParts := strings.Split(rangeInput, ":")
	
	// Convert range values to integers
	min, _ := strconv.Atoi(rangeParts[0])
	max, _ := strconv.Atoi(rangeParts[1])
	
	// TODO: Write your code below
	// 1. Define the Validator interface
	// 2. Create the ValidationError struct and implement Error() method
	// 3. Create the NumberValidator struct and implement Validate() method
	// 4. Process each number and validate it
	// 5. Display the results and summary
	
	// Display validation header
	fmt.Println("=== NUMBER VALIDATION SYSTEM ===")
	fmt.Printf("Validating numbers in range %d to %d\n", min, max)
	
	// Process each number here
	
	// Display validation summary
	fmt.Println("=== VALIDATION SUMMARY ===")
	// Add summary output here
	
	fmt.Println("Number validation completed successfully")
}