Hi, Gladly I did not totally remove my "singleton versions" of my models. I'll see this thread through and decide then what to do with my models.
-If there are this performance boost, it's a go-go for singletons -If there are too many (possible) problems, it's a no-go for singletons My models are just shared resources for dealing with some data (DbTables, Acl, Xml or whatever datasource). BUT if I'll go with the singletons, I need to get my head around state-issues on singletons. br, Marko Ed Lazor-3 wrote: > > Since I'm trying to get a better understanding, and since we seem to > be mixing several issues here, let me try to clarify and see if you > agree. > > As per Wiki, a global variable is a variable that is accessible in > every scope.... They are usually considered bad practice precisely > because of their nonlocality: a global variable can potentially be > modified from anywhere, (unless they reside in protected memory) and > any part of the program may depend on it. A global variable therefore > has an unlimited potential for creating mutual dependencies, and > adding mutual dependencies increases complexity. > > Singletons are considered bad practice, when used as a form of > universal data storage, because, like global variables, they have an > unlimited potential for creating mutual dependencies. > > I realize some people are saying that Singletons should never be used. > If that's the case, why are they used in Zend Framework? For > example, Zend_Auth, Zend_Registry, Zend_Loader_Autoloader, and > Zend_Controller_Front. Aren't these good examples of where Singletons > are beneficial? > > How do you know when it's ok to use Singletons? It seems like > Singletons are beneficial, when used to share a single resource, > because they have the potential for improving performance, and > reducing application complexity. > > Let me use Michael's Factory class as an example. Sure, you could > probably rename the class Singleton for clarity. In fact, the > getInstance method could be moved inside the class of the objects > being generated through the Factory class. > > To demonstrate this, you'd create a class called Users that extends > Zend_Db_Table and you'd give it a method called getInstance. Doing > this, you would effectively create a shared resource that serves as a > link to the Users database. Whenever you would use > > $Users = new Users(); > > You could instead use > > $Users = Users::getInstance(); > > That way, instead of reinstantiating an instance of Users all over the > application, you call getInstance and re-use the same object as often > as you'd like - giving the 7X performance boost Michael was > mentioning. > > And then, adding to the idea a little here, instead of manually adding > the getInstance method to every one of your Zend_Db_Table objects, you > could create a base class with this method that you can extend from. > Or, if you don't have PHP5.3, you can achieve the same thing by using > the Factory class that Michael presented. > > It might seem like a minor adjustment to use a common instance of a > Zend_Db_Table object when working with a specific table throughout > your application. If that 7X performance boost reduces your page load > from 49 seconds to 7 seconds, isn't it worth it? > > Yes - I realize there are other performance enhancements available as > well, cacheing, etc., but this one seems worthwhile also. Or... am I > just barking up the wrong tree and asking for trouble later on? > > Make sense? What do you think? Matthew? > > -Ed > > -- View this message in context: http://www.nabble.com/Models-as-Singletons-tp24575704p24639257.html Sent from the Zend Framework mailing list archive at Nabble.com.
