Angular的作用域Scope理解

要点之一：
父Scope里的基本类型的属性，子Scope创建时会复制它的值，新创建同名新属性，因此，在子Scope里改变属性值，不会影响父Scope里的属性值。

解决办法：

If you really want/need to use a primitive, there are two workarounds:

1.
Use $parent.parentScopeProperty in the child scope. This will prevent
the child scope from creating its own property.
2.
Define a function on the parent scope, and call it from the child, passing the primitive value up to the parent (not always possible)

https://github.com/angular/angular.js/wiki/Understanding-Scopes
有一篇中文也很好
http://xiaoyu2er.github.io/2016/01/23/angular-scope-in-depth/