From 735c7c4465a77d2953e9cb1328284e754f797db7 Mon Sep 17 00:00:00 2001
From: Stefan Majewsky <majewsky@gmx.net>
Date: Mon, 5 Feb 2018 22:06:18 +0100
Subject: apparently having a private member is not enough

---
 account.go   |  2 ++
 container.go | 11 ++++++++++-
 headers.go   | 27 +++++++++++++++++++++++++--
 3 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/account.go b/account.go
index 4438ce8..f4e8c07 100644
--- a/account.go
+++ b/account.go
@@ -117,6 +117,7 @@ func (a *Account) Invalidate() {
 //
 //A successful POST request implies Invalidate() since it may change metadata.
 func (a *Account) Update(headers AccountHeaders, opts *RequestOptions) error {
+	ensureInitializedByReflection(headers)
 	_, err := Request{
 		Method:            "POST",
 		Headers:           headers.ToHTTP(),
@@ -137,6 +138,7 @@ func (a *Account) Update(headers AccountHeaders, opts *RequestOptions) error {
 //
 //A successful PUT request implies Invalidate() since it may change metadata.
 func (a *Account) Create(headers AccountHeaders, opts *RequestOptions) error {
+	ensureInitializedByReflection(headers)
 	_, err := Request{
 		Method:            "PUT",
 		Headers:           headers.ToHTTP(),
diff --git a/container.go b/container.go
index e3b95d8..cfc0eab 100644
--- a/container.go
+++ b/container.go
@@ -96,6 +96,7 @@ func (c *Container) Headers() (ContainerHeaders, error) {
 //
 //A successful POST request implies Invalidate() since it may change metadata.
 func (c *Container) Update(headers ContainerHeaders, opts *RequestOptions) error {
+	ensureInitializedByReflection(headers)
 	_, err := Request{
 		Method:            "POST",
 		ContainerName:     c.name,
@@ -116,6 +117,7 @@ func (c *Container) Update(headers ContainerHeaders, opts *RequestOptions) error
 //
 //A successful PUT request implies Invalidate() since it may change metadata.
 func (c *Container) Create(headers ContainerHeaders, opts *RequestOptions) error {
+	ensureInitializedByReflection(headers)
 	_, err := Request{
 		Method:            "PUT",
 		ContainerName:     c.name,
@@ -137,7 +139,14 @@ func (c *Container) Create(headers ContainerHeaders, opts *RequestOptions) error
 //This operation fails with http.StatusNotFound if the container does not exist.
 //
 //A successful DELETE request implies Invalidate().
-func (c *Container) Delete(headers ContainerHeaders, opts *RequestOptions) error {
+func (c *Container) Delete(headers *ContainerHeaders, opts *RequestOptions) error {
+	if headers == nil {
+		h := NewContainerHeaders()
+		headers = &h
+	} else {
+		ensureInitializedByReflection(*headers)
+	}
+
 	_, err := Request{
 		Method:            "DELETE",
 		ContainerName:     c.name,
diff --git a/headers.go b/headers.go
index 44d0607..2d81ddf 100644
--- a/headers.go
+++ b/headers.go
@@ -19,6 +19,7 @@
 package schwift
 
 import (
+	"fmt"
 	"reflect"
 
 	"github.com/majewsky/schwift/headers"
@@ -29,6 +30,9 @@ import (
 //request on the account, and will be sent by a PUT or POST request. The other
 //attributes allow type-safe access to well-known headers, as noted in the tags
 //next to each field.
+//
+//Follow the link on the Headers attribute for the documentation of the Get(),
+//Set(), Del(), Clear() methods on this type.
 type AccountHeaders struct {
 	headers.Headers
 	BytesUsed      headers.Uint64Readonly `schwift:"X-Account-Bytes-Used"`
@@ -39,14 +43,18 @@ type AccountHeaders struct {
 	TempURLKey     headers.String         `schwift:"X-Account-Meta-Temp-URL-Key"`
 	TempURLKey2    headers.String         `schwift:"X-Account-Meta-Temp-URL-Key-2"`
 	//forbid initialization as struct literal (must use NewAccountHeaders)
-	private struct{}
+	initialized bool
 }
 
 //NewAccountHeaders prepares a new AccountHeaders instance.
+//
+//WARNING: Always use this function to construct AccountHeaders instances.
+//Failure to do so will result in uncontrolled crashes!
 func NewAccountHeaders() AccountHeaders {
 	var ah AccountHeaders
 	ah.Headers = make(headers.Headers)
 	initializeByReflection(&ah)
+	ah.initialized = true
 	return ah
 }
 
@@ -64,19 +72,26 @@ func (ah AccountHeaders) Validate() error {
 //request on the container, and will be sent by a PUT or POST request. The
 //other attributes allow type-safe access to well-known headers, as noted in
 //the tags next to each field.
+//
+//Follow the link on the Headers attribute for the documentation of the Get(),
+//Set(), Del(), Clear() methods on this type.
 type ContainerHeaders struct {
 	headers.Headers
 	Metadata headers.Metadata `schwift:"X-Container-Meta-"`
 	//TODO map well-known headers
 	//forbid initialization as struct literal (must use NewContainerHeaders)
-	private struct{}
+	initialized bool
 }
 
 //NewContainerHeaders prepares a new ContainerHeaders instance.
+//
+//WARNING: Always use this function to construct ContainerHeaders instances.
+//Failure to do so will result in uncontrolled crashes!
 func NewContainerHeaders() ContainerHeaders {
 	var ch ContainerHeaders
 	ch.Headers = make(headers.Headers)
 	initializeByReflection(&ch)
+	ch.initialized = true
 	return ch
 }
 
@@ -122,6 +137,14 @@ func validateByReflection(value interface{}) error {
 	})
 }
 
+func ensureInitializedByReflection(value interface{}) {
+	initialized := reflect.ValueOf(value).FieldByName("initialized").Bool()
+	if !initialized {
+		msg := "values of type %T MUST be initialized with the corresponding New...() function"
+		panic(fmt.Sprintf(msg, value, value))
+	}
+}
+
 func foreachTaggedField(value interface{}, callback func(fieldPtr interface{}, info fieldInfo) error) error {
 	rv := reflect.ValueOf(value).Elem()
 
-- 
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