cakePHP的目的是模型parentNode()函数?

I sometimes see the function parentNode() in cakePHP models. What is the purpose of that function and when should I use it? If I don't use it, what problems am I going to encounter.

On this website, they say that you need it so that your model can have ACL behaviors, but what if I just run the build_acl command after creating my Model, isn't that the same thing? Can someone shed some light on this please?

Thank you

build_acl() is useful as a one-time execution to populate your acl tables with the current controllers+actions. This is useful as a base to get you started.

parentNode() is called by the model behaviour in afterSave() to maintain the hiearchy during the life of your application. So when you manually (or dynamically) add AROs / ACOs later on (e.g. 5 months from now) everything will still work. Especially true if you add ACOs with custom aliases.

BTW, best ACL tutorial I've found:

http://net.tutsplus.com/tutorials/php/how-to-use-cakephps-access-control-lists/