How To Build Your First Project In Go

Exercise 1 of Gophercises - Build a terminal based Quiz game

Have you just started learning go?

Are you one of those who learn by doing projects?

Are you looking for a project to get your hands dirty with go?

With these questions in mind I started with my first project in Go. I started this after 1 day of going through the syntax of Go using Tour of Go in the official documentation.

That is when I came across Gophercises and started with the first exercise of it. Without much blabbering, lets break down the problem into high level steps and then search for each of them

How to read a local file?

  • Package os
  • I have used the os package but the Go by example provides another way of reading file as well. You can explore that as well
  • The Open method takes string file name or the absolute path as input and returns a File, if not then the second value is the error
  • We handle the error by checking if it is not nil and simply log out the error for our first project and dont do any error handling
// main.go
import (
    "os"
)

var filePath = "problems.csv"
file, err := os.Open(filePath)
if err != nil {
	log.Fatal(err)
}
  • We have seen how to read local file, but we still cant access the question since it is of type csv. We now look into how to parse the csv files and extract data in the next section

How to parse csv?

  • Package csv
  • The NewReader() method reads the file that we got from the os.Open()
  • The method returns an instance of type Reader.
  • The default delimiter is comma, but other can be specifed as well by modifying the Reader
reader := csv.NewReader(file)
questions, err := reader.ReadAll()
  • Now that we have the parsed csv file, we can ask these questions to the user and calculate the scores based on the answer provided by them

Score calculation

  • We have the question and answer pair as array of slices, where first value if the question and second is the correct answer
  • We define a score variable of type int
  • Then Loop through all the questions
  • The range returns two values. First is index and second is the slice consisting of question and answer (i.e each row in the csv file)
  • We also import the strconv package to convert the correct answer from csv file to be of type int, so that we can compare it with the value provided by the user.
  • To convert the string type to int, we use Atoi method.
  • The _ allows to us to not provide any variable name since we do not plan to use them
score := 0
var answer int
var correctAnswer int
for _, row := range questions {
	fmt.Println(row[0])
	fmt.Scanf("%d", &answer)
	correctAnswer, _ = strconv.Atoi(row[1])
	if answer == correctAnswer {
		score += 1
	}
}
  • Now that we have calculated the scores and we have the final answer in score variable. We will look at simply output them to the terminal

How to output to the terminal?

Package: fmt

  • The final score is stored in score variable
  • There are various output methods available. But for simplicity we use Print()
  • User input can be taken using Scanf
  • If you are already know c/c++, like me, you must already be familiar with printf and scanf. Go uses similar methods for output
  • For simplicity purpose, we just output the final score.
fmt.Print("Your score is",score)
  • Next we explore if we can dynamically provide the path of the csv file while running the command instead of defining a static file path in the code.

Command line flags

  • Package: flag
  • This package allows us to provide the csv file via the command line
  • We define a flag of type string with default value as problems.csv
  • The flag returns location to the file name provided by the user. So we use *fileName to read its value
var fileName = flag.String("csv", "problems.csv","a csv file in the format of 'question,answer' (default 'problems.csv')")
	flag.Parse()
	file, err := os.Open(*fileName)

Additional to see all flags available we can the following commands

go run main.go --help
// or
go run main.go -h
  • With this, the main goal of the project to design a quiz game with basic functionality is completed.
  • Lets take a break and come back to get do some more optimizations and additional exploration

What else can be do?

  • In this section, I compared my code to the official solution provided and found these things that could be done better.

  • Define a type of the problem 
    type problem struct{
  question string
  correctAnswer string
}
  • Invalid csv input. If the csv contains strings
import "strings"
for idx,row := range rows {
	data[idx] = problem{
		question: row[0],
		correctAnswer: strings.Trimspace(row[1]),
	}
}

Resources

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