Builder

package main

import (

        "fmt"

        "strconv"

        "strings"

)

// Rectangle is the proper data structure

type Rectangle struct {

        Height int

        Width  int

}

// Parse is the builder function, parsing the raw input from user

func Parse(raw string) *Rectangle {

        l := strings.Split(raw, ",")

        r := &Rectangle{

                height: -1,

                width:  -1,

        }

        if l[0] == "r" {

                r.height = convert(l[1])

                r.width = convert(l[2])

                return r

        }

        return nil

}

func convert(value string) int {

        v, err := strconv.Atoi(value)

        if err != nil {

                return -1

        }

        return v

}

// client interaction

func main() {

        r := Parse("r,5,10")

        if r == nil {

                fmt.Printf("r is nil\n")

                return

        }

        fmt.Printf("height: %v, width: %v\n", r.Height, r.Width)

}

// Output:

// height: 5, width: 10