errdata

README

errdata

errdata helps with associating some data to error classes.

Adding data

The Set function associates some data with some error class and key. For example:

var (
	Unauthorized = errs.Class("unauthorized")
	NotFound     = errs.Class("not found")
)

type httpErrorCodeKey struct{}

func init() {
	errdata.Set(Unauthorized, httpErrorCodeKey{}, http.StatusUnauthorized)
	errdata.Set(NotFound, httpErrorCodeKey{}, http.StatusNotFound)
}

Why do that? Get can read the associated data for an error if it was wrapped by any of the Classes you have set data on. For example:

func getStatusCode(err error) int {
	code, _ := errdata.Get(err, httpErrorCodeKey{}).(int)
	if code == 0 {
		code = http.StatusInternalServerError
	}
	return code
}

If the error has been wrapped by multiple classes for that key, the value for the most recently wrapped class is returned. For example:

func whatStatusCodeCode() {
	err := NotFound.Wrap(Unauthorized.New("test"))
	fmt.Println(getStatusCode(err))

	// output:
	// 404
}

Contributing

errdata is released under an MIT License. If you want to contribute, be sure to add yourself to the list in AUTHORS.

Documentation

Overview

Package errdata helps with associating some data to error classes

Index

• func Get(err error, key interface{}) interface{}
• func Set(class *errs.Class, key interface{}, value interface{})

Functions

func Get

func Get(err error, key interface{}) interface{}

Get returns the value associated to the key for the error if any of the classes the error is part of have a value associated for that key.

func Set

func Set(class *errs.Class, key interface{}, value interface{})

Set associates the value for the given key and class. Errors wrapped by the class will return the value in the call to Get for the key.