Learning GO : 08 - File Handling, Error Handling

Hey! I am Currently learning Go Lang, and I am taking some basic Notes on my Notion and though I'd also just publish them here. They are not well thought out or well written but it's just me taking notes from time to time for my reference.

I am taking the Udemy Course by Maximilian Schwarzmüller,

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Notes

Writing in Files

• the os package provides a function called WriteFile that takes in the name of the package, the data to be stored in the file and file mode, which will be the file modifying permissions.

func writeBalanceFiles(balance float64) {
    balanceText := fmt.Sprint(balance)
    os.WriteFile("balance.txt", []byte(balanceText), 0644)
}

Reading from a file

• sometimes when we are getting 2 return values from a function, we can then use a special variable name _ that means we want get the value but we dont want to use it.

data, _ := os.ReadFile("balance.txt")

• here the data will come with a byte type, so to handle that, we can only convert that data into a string
• we need the data string in float number, so for that we can use the strconv package, that gives us different methods to handle string operations
• we can use ParseFloat method, which will convert the string into floating number, with that we will need to provide the string value and bitSize which will be 32 or 64

func readFile() float64 {
    data, _ := os.ReadFile("balance.txt")
    balanceText := string(data)
    balance, _ := strconv.ParseFloat(balanceText, 64)
    return balance
}

• byte values cannot be directly converted into any type other then string and string value directly cannot be converted into any other type, that will require the use of strconv package

Error handling

• In GO, there is a special type as error that can be used to give out custom errors which comes from the built in errors package
• In GO, we can use nil to check the null value
• almost all packages provide an error as return value with a main value, we use the error to to check if there is nil value
• So, if the error is not nil that means there is an error and in that case we can give out some error response

    if err != nil {
        return 1000, errors.New("failed to find balance file")
    }

    var accountBalance, err = readFile()

    if err != nil {
        fmt.Println("ERROR")
        fmt.Println(err)
        fmt.Println("===============")
    }

Panic!

• there is an in built method called panic() that will stop the program execution and give out special error

    if err != nil {
        fmt.Println("ERROR")
        fmt.Println(err)
        fmt.Println("===============")
        panic("Can't Continue Sorry!")
    }