Construction/Destruction Order of QObjects

int main()
{

     QPushButton quit("Quit");

     QWidget window;

     quit.setParent(&window);

     ...

 }

In this case, the order of destruction causes a problem. The parent's destructor is called first because it was created last. It then calls the destructor of its child, quit, which is incorrect because quit is a local variable. When quit subsequently goes out of scope, its destructor is called again, this time correctly, but the damage has already been done.

Remember: When the destructor of the child(quit) is called first, it removes itself from its parent(window), before the destructor of parent is called. Anyway the child will not be called twice. You MUST "delete" the object manually which is created with "New" and don't have a parent!

Reading Qt 4.4 Tutorial 1

• The QApplication object must be created before any GUI-related features of Qt are used.

•     QPushButton hello("Hello world!");

  A push button is created. Because we don't specify a parent window (as second argument to the QPushButton constructor), the button will be a window of its own, with its own window frame and title bar.
• The button's size is determined by its default size hint. We could call QWidget::move() to assign a specific screen position to the widget, but instead we let the windowing system choose a position.

•     hello.show();

  A widget is never visible when you create it. You must call QWidget::show() to make it visible.

•    return app.exec();

  This is where main() passes control to Qt
  

  int QApplication::exec ()

  Enters the main event loop and waits until exit() is called, then returns the value that was set to exit() (which is 0 if exit() is called via quit()).

• 基本把教程上的COPY下来了，细节注意到了却影响到整体阅读速度，在博客上修改这破格式花了不少时间。
  
  
  

C++ STL1

用起瘾了，不好不好，忽略了具体实现和基本功，所谓理由是更能把精力放在算法上。。
不多总结，具体使用方法参见 http://www.cplusplus.com/reference/
今天收获是关键字排序，参见 一个多关键字排序例子
其中ICmpMuls也可直接放MultiData中，bool operator() 重载圆括号，sort第三个参数具体机理还很茫然(updated: 函数指针)，以后如果将C++作为主语言，熟练后一定要读读STL源码剖析那本书。

qt1

1.

通过使用一个layout管理器对旋转窗口和滑块窗口进行了布局设置。一个布局管理者就是一个根据窗口作用设置其大小和位置的对象。Qt有三个主要的布局管理类：

QHBoxLayout：将窗口部件水平自左至右设置（有些情况下是自右向左）。

QVBoxLayout：将窗口部件垂直自上向下设置。

QGridLayout： 以网格形式设置窗口部件。

调用QWidget::setLayout()函数在对象window上安装布局管理器。通过这个调用,部件自动成为布局管理器所在窗口的子窗口。

2.

Qt程序员最常用的设计模式是：说明所需要的窗口部件，然后设置这些部件必须的特性。程序员把窗口部件添加到布局管理器中，布局管理器就将自动地设置这些部件的大小和位置。而用户界面的行为是通过连接各个部件（运用信号SIGNAL/槽SLOT机制）来实现的。