静态,静态的意义是只初始化一次,因为静态全局变量只能在一个文件中使用。
而普通的全局变量则可以在多个文件中使用。
200w相机的ip是243
500w相机的ip是244
纯虚函数是为了说明基类是一个接口,基类不做实现。
虚函数是为了说明,基类已经做了一个缺省实现,但是这种行为具备一定的危险性----就是一些需要自定义的方法,不了解的人也用缺省性行为完成。
那么就需要纯虚函数提供实现,以让子类明确调用-----这样一来,以纯虚函数是为了说明基类是一个接口矛盾了?
而非虚函数则是为派生类提供一种强制性的实现。
Navigating the current page: ? show the help dialog for a list of all available keys h scroll left j scroll down k scroll up l scroll right gg scroll to top of the page G scroll to bottom of the page d scroll down half a page u scroll up half a page f open a link in the current tab F open a link in a new tab r reload gs view source zi zoom in zo zoom out i enter insert mode -- all commands will be ignored until you hit esc to exit yy copy the current url to the clipboard gf cycle forward to the next frame Using find: / enter find mode -- type your search query and hit enter to search or esc to cancel n cycle forward to the next find match N cycle backward to the previous find match Navigating your history: H go back in history L go forward in history Manipulating tabs: J, gT go one tab left K, gt go one tab right t create tab x close current tab X restore closed tab (i.e. unwind the 'x'…
来源:https://www.cnblogs.com/xianqingzh/archive/2011/03/25/1995119.html