README
¶
Introduction
Xyerror contains special errors that are good for error comparison and
debugging.
This package is inspired by idea of Python Exception.
Features
Python Exception Idea
Xyerror defined an error type used to create other errors called Class, it is
equivalent to Exception class in Python.
Class creates XyError objects by using New method. It looks like
Exception class creates Exception instances. Example:
// xyerror
var xerr xyerror.XyError
xerr = xyerror.ValueError.New("value is invalid")
fmt.Println(xerr)
# python
print(ValueError("value is invalid"))
A Class can "inherits" from another Class. Example:
// xyerror
var ZeroDivisionError = xyerror.ValueError.NewClass("ZeroDivisionError")
fmt.Println(ZeroDivisionError.New("do not divide by zero"))
# python
class ZeroDivisionError(ValueError):
...
print(ZeroDivisionError("do not divide by zero"))
A Class also "inherits" from some Class instances. Example:
// xyerror
var ValueTypeError = xyerror.
Combine(xyerror.ValueError, xyerror.TypeError).
NewClass("ValueTypeError")
# python
class ValueTypeError(ValueError, TypeError):
...
A XyError created by Class can compare to this Class.
// xyerror
func foo() error {
return xyerror.ValueError.New("value is invalid")
}
func bar() error {
if xerr := foo(); errors.Is(xerr, xyerror.ValueError) {
fmt.Println(xerr)
} else {
return xerr
}
return nil
}
# python
def foo():
raise ValueError("value is invalid")
def bar():
try:
foo()
except ValueError as e:
print(e)
Error number
Every Class has its own unique number called Errno. This number is used to
compare a XyError with a Class. All XyError instances created by the same
Class have the same errno.
Module-oriented Error
Xyerror is tended to create module-oriented errors. Errno of all Class
instances in a module need to be the same prefix.
For example, ValueError and TypeError are in Default module. So their
errno should be 100001 and 100002, respectively. In this case, 100000 is the
prefix number of Default module.
Every module needs to create an object called Generator to create its error
Class instances. Prefix of module is a self-defined value, it must be
divisible by 100000 and not equal to other modules' prefix.
var egen = xyerror.Register("XyExample", 200000)
var (
FooError = egen.NewClass("FooError")
BarError = egen.NewClass("BarError")
)
Visit pkg.go.dev for more details.
Example
package xyerror_test
import (
"errors"
"fmt"
"github.com/xybor/xyplatform/xyerror"
)
var exampleGen = xyerror.Register("example", 400000)
func ExampleClass() {
// To create a root Class, call Generator.NewClass with the name of Class.
var RootError = exampleGen.NewClass("RootError")
// You can create a class from another one.
var ChildError = RootError.NewClass("ChildError")
fmt.Println(RootError)
fmt.Println(ChildError)
// Output:
// [400001] RootError
// [400002] ChildError
}
func ExampleXyError() {
// You can compare a XyError with an Class by using the built-in method
// errors.Is.
var NegativeIndexError = xyerror.IndexError.NewClass("NegativeIndexError")
var err1 = xyerror.ValueError.New("some value error")
if errors.Is(err1, xyerror.ValueError) {
fmt.Println("err1 is a ValueError")
}
if !errors.Is(err1, NegativeIndexError) {
fmt.Println("err1 is not a NegativeIndexError")
}
var err2 = NegativeIndexError.New("some negative index error")
if errors.Is(err2, NegativeIndexError) {
fmt.Println("err2 is a NegativeIndexError")
}
if errors.Is(err2, xyerror.IndexError) {
fmt.Println("err2 is a IndexError")
}
if !errors.Is(err2, xyerror.ValueError) {
fmt.Println("err2 is not a ValueError")
}
// Output:
// err1 is a ValueError
// err1 is not a NegativeIndexError
// err2 is a NegativeIndexError
// err2 is a IndexError
// err2 is not a ValueError
}
func ExampleGroup() {
// Group allows you to create a class with multiparents.
var KeyValueError = xyerror.
Combine(xyerror.KeyError, xyerror.ValueError).
NewClass(exampleGen, "KeyValueError")
var err = KeyValueError.New("something is wrong")
if errors.Is(err, xyerror.KeyError) {
fmt.Println("err is a KeyError")
}
if errors.Is(err, xyerror.ValueError) {
fmt.Println("err is a ValueError")
}
// Output:
// err is a KeyError
// err is a ValueError
}
Documentation
¶
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
var ( UnknownError = defaultGen.NewClass("UnknownError") IOError = defaultGen.NewClass("IOError") FloatingPointError = defaultGen.NewClass("FloatingPointError") IndexError = defaultGen.NewClass("IndexError") KeyError = defaultGen.NewClass("KeyError") NotImplementedError = defaultGen.NewClass("NotImplementedError") ValueError = defaultGen.NewClass("ValueError") ParameterError = defaultGen.NewClass("ParameterError") TypeError = defaultGen.NewClass("TypeError") AssertionError = defaultGen.NewClass("AssertionError") )
Functions ¶
Types ¶
type Class ¶
type Class struct {
// contains filtered or unexported fields
}
Class is a special error with error number and error name. Error number is a unique number of Class and helps to determine which module the error Class belongs to.
The main purpose of error Class is creating a XyError, so that it should not be used for returning.
A Class can be created by one or many parent Classes. The Class without parent is called root Class..
Example ¶
package main
import (
"fmt"
"github.com/xybor/xyplatform/xyerror"
)
var exampleGen = xyerror.Register("example", 400000)
func main() {
// To create a root Class, call Generator.NewClass with the name of Class.
var RootError = exampleGen.NewClass("RootError")
// You can create a class from another one.
var ChildError = RootError.NewClass("ChildError")
fmt.Println(RootError)
fmt.Println(ChildError)
}
Output: [400001] RootError [400002] ChildError
type Generator ¶
type Generator struct {
// contains filtered or unexported fields
}
Generator is used to generate root Class for every module. It is determined by the identifier of module.
type Group ¶
type Group []Class
Example ¶
package main
import (
"errors"
"fmt"
"github.com/xybor/xyplatform/xyerror"
)
var exampleGen = xyerror.Register("example", 400000)
func main() {
// Group allows you to create a class with multiparents.
var KeyValueError = xyerror.
Combine(xyerror.KeyError, xyerror.ValueError).
NewClass(exampleGen, "KeyValueError")
var err = KeyValueError.New("something is wrong")
if errors.Is(err, xyerror.KeyError) {
fmt.Println("err is a KeyError")
}
if errors.Is(err, xyerror.ValueError) {
fmt.Println("err is a ValueError")
}
}
Output: err is a KeyError err is a ValueError
type XyError ¶
type XyError struct {
// contains filtered or unexported fields
}
XyError is an error supporting to check if an error belongs to a class or not.
errors.Is(err, cls) returns true if err is created by cls itself or cls's child class.
Example ¶
package main
import (
"errors"
"fmt"
"github.com/xybor/xyplatform/xyerror"
)
func main() {
// You can compare a XyError with an Class by using the built-in method
// errors.Is.
var NegativeIndexError = xyerror.IndexError.NewClass("NegativeIndexError")
var err1 = xyerror.ValueError.New("some value error")
if errors.Is(err1, xyerror.ValueError) {
fmt.Println("err1 is a ValueError")
}
if !errors.Is(err1, NegativeIndexError) {
fmt.Println("err1 is not a NegativeIndexError")
}
var err2 = NegativeIndexError.New("some negative index error")
if errors.Is(err2, NegativeIndexError) {
fmt.Println("err2 is a NegativeIndexError")
}
if errors.Is(err2, xyerror.IndexError) {
fmt.Println("err2 is a IndexError")
}
if !errors.Is(err2, xyerror.ValueError) {
fmt.Println("err2 is not a ValueError")
}
}
Output: err1 is a ValueError err1 is not a NegativeIndexError err2 is a NegativeIndexError err2 is a IndexError err2 is not a ValueError
Source Files