Error interface in Go - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the Error interface in Go?

The Error interface in Go is a built-in interface used to represent errors. It has a single method Error() string that returns a descriptive error message.

intermediate

How do you create a custom error type in Go?

You create a custom error type by defining a type and implementing the Error() string method for it. This makes your type satisfy the error interface.

beginner

What does the errors.New function do?

The errors.New function creates a simple error with a given message string. It returns a value that satisfies the error interface.

beginner

Why is it useful to use the error interface in Go functions?

Using the error interface allows functions to return detailed error information in a consistent way. It helps the caller handle errors gracefully and understand what went wrong.

beginner

What is the signature of the Error() method in the error interface?

The signature is Error() string. It returns a string describing the error.

What method must a type implement to satisfy the Go error interface?

A Error() int

B String() error

C Message() string

D Error() string

The error interface requires the method Error() string.

Which package provides the New function to create simple errors?

A errors

B io

C fmt

D strings

The errors package provides New to create basic error values.

What does the Error() method return?

A An integer error code

B A string describing the error

C Nothing (void)

D A boolean indicating success

The Error() method returns a string describing the error.

Why use the error interface instead of just strings for errors?

A To provide more structured error information

B Because strings are slower

C Because Go does not support strings

D To avoid using functions

The error interface allows more structured and flexible error handling than plain strings.

How do you check if a function returned an error in Go?

A if err == false

B if err == 0

C if err != nil

D if err == ""

In Go, errors are checked by comparing to nil: if err != nil means an error occurred.

Explain what the Go error interface is and why it is important.

Think about how Go functions communicate problems.

Describe how to create a custom error type in Go and why you might want to do that.

Consider when simple error messages are not enough.