Initialization of variable was never used; consider replacing with assignment to ‘_’ or removing it 刚接触iOS的swift语言,还没来得及看视频,自己随意定义了一个常量,结果报警告. 其实不用着急,这个提示信息是告诉你定义的这个常量你没有使用到. 接下来使用它,警告信息就会消失.

If we choose an associative container, we’ll almost certainly be using a balanced binary tree. Such a tree would be made up of tree nodes. each holding not only a Widget, but also a pointer to the nod