关于本节内容的几个问题（见代码中的注释）

老师好，根据老师上课讲解的内容，我进行了实现，在实现的过程中有三处地方不太明白，已经在代码中对应的位置标注出，还请老师指点！谢谢老师！

#include <QtCore/QCoreApplication>
#include "HttpAccess.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

	HttpAccess httpAccess;
	// 问题1：这里lambda表达式是如何通过信号拿到参数data的？
	QObject::connect(&httpAccess, &HttpAccess::finished, [&](const QByteArray& data)
	{
		qDebug() << data;
	});

	httpAccess.Get(QUrl("http://www.baidu.com"));

    return a.exec();
}

#pragma once
#include <QObject>
#include <QtNetwork/QtNetwork>

class HttpAccess : public QObject
{
	Q_OBJECT
public:
	explicit HttpAccess(QObject *parent = nullptr);
	HttpAccess(const HttpAccess& other) = delete;
	HttpAccess(const HttpAccess&& other) = delete;

	HttpAccess& operator=(const HttpAccess& other) = delete;
	HttpAccess& operator=(const HttpAccess&& other) = delete;

	virtual ~HttpAccess();

	void Get(const QUrl& url);

signals:
	// 问题2：这个finished在哪里实现的？
	void finished(const QByteArray& data);

private:
	QNetworkAccessManager m_manager;
};

#include "HttpAccess.h"

HttpAccess::HttpAccess(QObject* parent) : QObject(parent)
{
	
}

void HttpAccess::Get(const QUrl& url)
{
	const QNetworkRequest request(url);
	QNetworkReply* reply = m_manager.get(request);
	// 问题3：这里reply为什么会在connect执行完成之前失效？
	connect(reply, &QNetworkReply::finished, [=]()
	{
		if(reply->error() == QNetworkReply::NoError)
		{
			QByteArray data = reply->readAll();
			emit finished(data);
		}
	});
}

HttpAccess::~HttpAccess()
{
	
}