How can I set a panic in anchor?

Question

How can I modify this Anchor tutorial code in a way so when any non-authority wallet tries to update the count variable it will give a message with an error like only owner can modify the value?

Answer 1

First, you need to create an error, the message will be sent when the error is thrown

#[error_code]
pub enum ErrorCode {
    #[msg("This is an ERROR!")]
    MyCustomError,
}

then in your instruction

if something_is_wrong {
    return Err(error!(ErrorCode::DrawAlreadyOffered));
}