之前使用c++开发的程序都是使用curl库进行各种http操作。
qt为我们继承了一些网络操作的类，因此不需要第三方库的支持了。今天就跟大家分享一下qt中对http请求的封装。
其中用到了：
QNetworkRequest
The QNetworkRequest class holds a request to be sent with QNetworkAccessManager.
http://doc.qt.io/qt-4.8/qnetworkrequest.html#details
QNetworkAccessManager
The QNetworkAccessManager class allows the application to send network requests and receive replies.
http://doc.qt.io/qt-5/qnetworkaccessmanager.html#details
QNetworkReply
The QNetworkReply class contains the data and headers for a request sent with QNetworkAccessManager.
http://doc.qt.io/qt-5/qnetworkreply.html#details
这里不再过多的介绍上面三个类，因为qt的文档描述的非常非常的清楚。
开始写我们自己的http api：
写一个基类，命名为BaseAPI:
baseapi.h
#ifndef BASEAPI_H#define BASEAPI_H#include <QSettings>#include <QNetworkRequest>#include <QNetworkReply>#include <QNetworkAccessManager>#include "base/constants.h"class BaseAPI : public QObject{Q_OBJECTpublic:BaseAPI();~BaseAPI();void get(const QString url);void post(const QString url, const QByteArray &data);protected:virtual void requestFinished(QNetworkReply *reply, const QByteArray data, const int statusCode) = 0;public slots:void serviceRequestFinished(QNetworkReply *reply);private:QNetworkRequest httpRequest;QNetworkAccessManager networkAccessManager;QSettings *settings;};#endif // BASEAPI_H
#include "baseapi.h"BaseAPI::BaseAPI(){httpRequest.setRawHeader("Accept", API_ACCEPT);httpRequest.setRawHeader("User-Agent", API_USER_AGENT);httpRequest.setRawHeader("X-XXX-API-Key", API_KEY);httpRequest.setRawHeader("X-XXX-API-Secret", API_SECRET);httpRequest.setRawHeader("Accept-Encoding", "gzip, deflate");httpRequest.setRawHeader("Content-Type", "application/json");settings = new QSettings("XXX");QString id = settings->value(SETTING_ACCOUNT_ID, "").toString();QString token = settings->value(SETTING_ACCOUNT_TOKEN, "").toString();if(!id.isEmpty()) {httpRequest.setRawHeader("X-XXX-User-ID", id.toStdString().c_str());}if (!token.isEmpty()) {httpRequest.setRawHeader("X-XXX-User-Token", token.toStdString().c_str());}qDebug() << "BaseAPI...id:" << id << " token:" + token;QObject::connect(&networkAccessManager, SIGNAL(finished(QNetworkReply*)), this, SLOT(serviceRequestFinished(QNetworkReply*)));}BaseAPI::~BaseAPI(){networkAccessManager.disconnect();if (settings){delete settings;settings = nullptr;}}void BaseAPI::get(const QString url){httpRequest.setUrl(QUrl(url));networkAccessManager.get(httpRequest);}void BaseAPI::post(const QString url, const QByteArray &data){httpRequest.setUrl(QUrl(url));networkAccessManager.post(httpRequest, data);}void BaseAPI::serviceRequestFinished(QNetworkReply *reply){int statusCode = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();qDebug() << "BaseAPI...serviceRequestFinished...statusCode:" << statusCode;if(reply->error() == QNetworkReply::NoError) {requestFinished(reply, reply->readAll(), statusCode);} else {requestFinished(reply, "", statusCode);}// At the end of that slot, we won't need it anymorereply->deleteLater();}
解释：
1 使用了qt中的QSettings，就是一个存储功能
The QSettings class provides persistent platform-independent application settings
http://doc.qt.io/qt-4.8/qsettings.html
2 声明了一个纯虚函数，使得子类根据自己的情况进行重写
基类就这样写完了，下面写一个应用，比如从服务器请求游戏列表：
写一个子类GameAPI继承自BaseAPI：
gameapi.h
#ifndef GAMEAPI#define GAMEAPI#include <functional>#include <QList>#include <QPair>#include "baseapi.h"class GameAPI: public BaseAPI{public:GameAPI();~GameAPI();void getGameList(std::function<void(bool, QList<QPair<QString,QString>>)> callback);protected:void requestFinished(QNetworkReply* reply, const QByteArray data, const int statusCode);private:std::function<void(bool, QList<QPair<QString,QString>>)> checkCallback;};#endif // GAMEAPI
#include "gameapi.h"#include "qdebug.h"#include <QJsonArray>#include <QJsonObject>#include <QJsonDocument>const QString GET_GAME = QString("").append("/apps");GameAPI::GameAPI(){}GameAPI::~GameAPI(){}void GameAPI::requestFinished(QNetworkReply* reply, const QByteArray data, const int statusCode){if (statusCode == 200) {QJsonParseError jsonError;QJsonArray json_array = QJsonDocument::fromJson(data, &jsonError).array();if(jsonError.error == QJsonParseError::NoError) {QList<QPair<QString,QString>> games;for(int i = 0; i < json_array.size(); ++i) {QJsonObject json = json_array.at(i).toObject();games.append(qMakePair(json.value("key1").toString(), json.value("key2").toString()));}this->checkCallback(true, games);return;}}QList<QPair<QString,QString>> games;this->checkCallback(false, games);}void GameAPI::getGameList(std::function<void(bool, QList<QPair<QString,QString>>)> callback){this->checkCallback = callback;get(GET_GAME);}
使用接口：
GameAPI game_api = new GameAPI();game_api->getGameList([&](bool success, QList<QPair<QString,QString>> games){if (success){//do something}});
