add Is/Equal/Unwrap functions for package gerror

errors/gerror/gerror_error_code.go

@@ -0,0 +1,31 @@
+// Copyright GoFrame Author(https://goframe.org). All Rights Reserved.
+//
+// This Source Code Form is subject to the terms of the MIT License.
+// If a copy of the MIT was not distributed with this file,
+// You can obtain one at https://github.com/gogf/gf.
+
+package gerror
+
+import (
+	"github.com/gogf/gf/v2/errors/gcode"
+)
+
+// Code returns the error code.
+// It returns CodeNil if it has no error code.
+func (err *Error) Code() gcode.Code {
+	if err == nil {
+		return gcode.CodeNil
+	}
+	if err.code == gcode.CodeNil {
+		return Code(err.Next())
+	}
+	return err.code
+}
+
+// SetCode updates the internal code with given code.
+func (err *Error) SetCode(code gcode.Code) {
+	if err == nil {
+		return
+	}
+	err.code = code
+}