Equal Comparison Method

Error objects support comparison, and the Equal method is used to fully determine whether two errors are the same. This is mainly achieved through the following method:

// Equal reports whether current error `err` equals to error `target`.
// Please note that, in default comparison for `Error`,
// the errors are considered the same if both the `code` and `text` of them are the same.
func Equal(err, target error) bool

Interface Definition

If a custom error data structure needs to support comparison, the custom error structure needs to implement the following interface:

// IEqual is the interface for Equal feature.
type IEqual interface {
    Error() string
    Equal(target error) bool
}

Error objects created by the GoFrame framework's error component already implement this interface, and the component's default comparison logic checks the error code and error message.

info

Note that if both errors do not carry error codes and their error messages are the same, the component considers the two errors to be the same.

Usage Example

func ExampleEqual() {
    err1 := errors.New("permission denied")
    err2 := gerror.New("permission denied")
    err3 := gerror.NewCode(gcode.CodeNotAuthorized, "permission denied")
    fmt.Println(gerror.Equal(err1, err2))
    fmt.Println(gerror.Equal(err2, err3))

    // Output:
    // true
    // false
}

Is Inclusion Judgment

Error objects support inclusion judgment. The Is method is used to determine whether the given error is in a specified error chain (if the error carries a stack, it will be judged recursively). This is mainly achieved through the following method:

// Is reports whether current error `err` has error `target` in its chaining errors.
// It is just for implements for stdlib errors.Unwrap from Go version 1.17.
func Is(err, target error) bool

Usage Example

func ExampleIs() {
    err1 := errors.New("permission denied")
    err2 := gerror.Wrap(err1, "operation failed")
    fmt.Println(gerror.Is(err1, err1))
    fmt.Println(gerror.Is(err2, err2))
    fmt.Println(gerror.Is(err2, err1))
    fmt.Println(gerror.Is(err1, err2))

    // Output:
    // false
    // true
    // true
    // false
}