前言

做實驗，想向chromium工程的類中加入一個成員變數，結果出現如下編譯錯誤：

WeakPtrFactory members which refer to their outer class must be the last member in the outer class definition

沒想到是啥錯誤，其實錯誤提示也很明顯。
後來看看類有沒有WeakPtrFactory型別的成員變數，真有啊，將自己定義的新變數，放在他上面就行。說明，如果類中有WeakPtrFactory型別的成員變數，必須是類中最後一個成員變數. autoninja檢查的挺嚴格的。

實驗

// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CHROME_BROWSER_UI_WEBUI_DOWNLOAD_INTERNALS_DOWNLOAD_INTERNALS_UI_MESSAGE_HANDLER_H_
#define CHROME_BROWSER_UI_WEBUI_DOWNLOAD_INTERNALS_DOWNLOAD_INTERNALS_UI_MESSAGE_HANDLER_H_

#include <string>
#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "components/download/public/background_service/logger.h"
#include "content/public/browser/web_ui_message_handler.h"

// Z:\chromium\src\url\gurl.h
#include "url/gurl.h"

namespace download {
class DownloadService;
}

namespace download_internals {

// Class acting as a controller of the chrome://download-internals WebUI.
class DownloadInternalsUIMessageHandler : public content::WebUIMessageHandler,
                                          public download::Logger::Observer {
 public:
  DownloadInternalsUIMessageHandler();
  ~DownloadInternalsUIMessageHandler() override;

  // content::WebUIMessageHandler implementation.
  void RegisterMessages() override;

  // download::Logger::Observer implementation.
  void OnServiceStatusChanged(const base::Value& service_status) override;
  void OnServiceDownloadsAvailable(
      const base::Value& service_downloads) override;
  void OnServiceDownloadChanged(const base::Value& service_download) override;
  void OnServiceDownloadFailed(const base::Value& service_download) override;
  void OnServiceRequestMade(const base::Value& service_request) override;

 private:
  // Get the current DownloadService and sub component statuses.
  void HandleGetServiceStatus(const base::ListValue* args);
  void HandleGetServiceDownloads(const base::ListValue* args);

  // Starts a background download.
  void HandleStartDownload(const base::ListValue* args);
	void HandleStartDownload_url(GURL& url);

	bool get_string_value_by_key_from_value(const base::Value& value, const char* psz_key, std::string& str_value);
	bool get_double_value_by_key_from_value(const base::Value& value, const char* psz_key, double& f_value);

private:
  download::DownloadService* download_service_;

	// base::WeakPtrFactory<>型別的成員變數必須是本類的最後一個成員變數
	// 成員變數如果是類, 必須加在base::WeakPtrFactory型別成員變數的上面，否則報錯如下
	// WeakPtrFactory members which refer to their outer class must be the last member in the outer class definition
	std::string m_str_url_by_js_first; // 儲存第一次js發來的url

	base::WeakPtrFactory<DownloadInternalsUIMessageHandler> weak_ptr_factory_;

	DISALLOW_COPY_AND_ASSIGN(DownloadInternalsUIMessageHandler);
};

}  // namespace download_internals

#endif  // CHROME_BROWSER_UI_WEBUI_DOWNLOAD_INTERNALS_DOWNLOAD_INTERNALS_UI_MESSAGE_HANDLER_H_