Several ways of Qt signal slot connection

1. Standard writing

    connect(ui->pushButton,SIGNAL(clicked()),this,SLOT(onBtnClicked()));

2. How to write address function pointer

Get type checking at compile time

    connect(ui->pushButton,&QPushButton::clicked,this,&Widget::onBtnClicked);

3. How to write lambda expressions

    connect(ui->pushButton,&QPushButton::clicked,this,[=]{
        qDebug() << "clicked";
    });