Custom error types in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a custom error type named MyError.

Go

type MyError struct {
	message string
}

func (e *MyError) Error() string {
	return [1]
}

Drag options to blanks, or click blank then click option'

Ae.message

Bmessage

Cerror

De

Attempts:

3 left

💡 Hint

Common Mistakes

Returning the variable name 'message' instead of the field value.

Returning the receiver 'e' directly instead of a string.

The Error() method must return the error message string stored in the struct field message. We access it with e.message.

2fill in blank

medium

Complete the code to create a new MyError instance with the message "something went wrong".

Go

func NewMyError() error {
	return &MyError{message: [1]
}

Drag options to blanks, or click blank then click option'

A"error occurred"

B"something went wrong"

Csomething went wrong

Derror

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting quotes around the string.

Using a variable name instead of a string literal.

The message field must be a string literal with quotes. So we use "something went wrong".

3fill in blank

hard

Fix the error in the code by completing the blank to implement the error interface.

Go

type MyError struct {
	msg string
}

func (e MyError) [1]() string {
	return e.msg
}

Drag options to blanks, or click blank then click option'

AMessage

BErrorMsg

CError

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name other than Error.

Using a pointer receiver instead of value receiver (both work but here value is used).

The error interface requires the method Error() that returns a string.

4fill in blank

hard

Fill both blanks to create a function that returns a formatted MyError with a dynamic message.

Go

func NewFormattedError(code int, msg string) error {
	return &MyError{message: fmt.Sprintf([1], [2], msg)}
}

Drag options to blanks, or click blank then click option'

A"Error %d: %s"

Bcode

Cmsg

D"%s %d"

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the order of format specifiers and arguments.

Using incorrect format specifiers.

The format string should be "Error %d: %s" and the first argument is the integer code.

5fill in blank

hard

Fill both blanks to check if an error is of type *MyError and print its message.

Go

func CheckError(err error) {
	var e *MyError
	if [1](err, &e) {
		fmt.Println(e.[2]())
	} else {
		fmt.Println("Not a MyError")
	}
}

Drag options to blanks, or click blank then click option'

Aerrors.As

BError

DError()

Attempts:

3 left

💡 Hint

Common Mistakes

Using type assertion syntax instead of errors.As function.

Calling the wrong method or missing parentheses.

Use errors.As to check error type and call Error() method to get the message.