qt中自定义槽函数怎么调用该类中的控件指针

Question

就是想把lineEdit里面的值在slider里面显示，
就是在我自定义的槽函数里面调用了构造函数中的控件指针，结果显示的是野指针，请问我应该怎么改
部分代码如下：

//widget.h
class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = 0);
    ~Widget();
    QSlider *slider;
    QLineEdit *edit;
public slots:
    void ChangeValue();

};

//widget.cpp  控件的布局什么的，还定义了一个定时器，定时触发槽函数
Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    QLineEdit *edit = new QLineEdit("25");
    QSlider *slider = new QSlider(Qt::Vertical);
    slider->setRange(0,100);
    slider->setValue(0);
    slider->setTickPosition(QSlider::TicksLeft);

    QLabel *label = new QLabel("0");

    QHBoxLayout *cLayout = new QHBoxLayout;
    cLayout->addWidget(label,0,Qt::AlignRight);
    cLayout->addWidget(slider,0,Qt::AlignLeft);

    QVBoxLayout *mainLayout = new QVBoxLayout;
    mainLayout->addWidget(edit);
    mainLayout->addLayout(cLayout);
    setLayout(mainLayout);

    slider->setFocus();

    QTimer *timer1 = new QTimer();
    timer1->setInterval(500);
    timer1->start();

    connect(slider,SIGNAL(valueChanged(int)),label,SLOT(setNum(int)));
    connect(timer1,SIGNAL(timeout()),this,SLOT(ChangeValue()));
} 
Widget::~Widget(){}
void Widget::ChangeValue(){
    QString s = edit->text();
    int value = s.toInt();
    slider->setValue(value);
}