Norm Scherer wrote in post #1102294: > On 03/18/2013 10:37 AM, John Merlino wrote: >> Is there a good practice when to use the session variable. Sometimes I >> find myself using both the session variable and instance variable. For >> example, I have a table that allows a user to select a date. I store >> the date both in the session and in the instance variable. Should I >> not bother to store it in session? In what situations should you use >> the session variable? -- > The rails session persists across requests while instance variables do > not. If you need something in a following request it (or a reference) > must be in the session. If you do not need it later I always use an > instance variable.
I wouldn't say that this is precisely accurate. You could continue passing a variable from one request to another, and to third, and so on. Session variables are useful when you really need a value to persist for the entire session. I would also say that it's good practice to use session variable sparingly. Session variables are somewhat akin to global variables in the sense that they represent globally accessible shared state (at least within the context of the current session). Session variables are also long lived, taking up memory as long as the session is kept alive. Although in a Rails application sessions are torn down and recreate upon every request, but that might even be worse than just leaving them in memory between requests. Another thing to keep in mind is that by default Rails uses a cookie based session storage mechanism, which means sessions have a hard 4K limit (cookies are limited to 4K by spec). Another reason to avoid putting large amounts of data in the session. A typical use case for session variable are things like the "id" of the current user. Notice I said the "id" not the user object itself. It's better to load the user object when, and only when, necessary. There are other great uses for session variables, but think twice about if it's really necessary and try to keep the amount of data as small as possible. Remember for every variable in the session is just one more thing that has to be loaded from persistent storage on every single request. -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To unsubscribe from this group and stop receiving emails from it, send an email to rubyonrails-talk+unsubscr...@googlegroups.com. To post to this group, send email to rubyonrails-talk@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
