[Rails] Re: How do I access a variable defined in application.rb from within application.rhtml?
Thanks, this sounds like what I need. On Feb 22, 7:24 pm, Jeff Lewis wrote: > To initialize some db-read var (tidbit in your example) that would > survive and be callable for each subsequent app request, you'll want > to do so via lazy-initialization using a before_filter (mentioned by > bill) in application.rb. > > How you store such lazy-init vars between requests depends on the > scope/use of such vars by users/requests of the app: > > If the var that you're setting is specific to some user alone, and > should not be shared by all users' requests, then you could store that > var in the user's session: > > # in ./app/controller/application.rb > ... > before_filter :do_lazy_init > > ... > private > > def do_lazy_init > session[:tidbit] = Tidbit.random if not session[:tidbit] > @tidbit = session[:tidbit] > end > > which all of your app controller meths and view templates could then > use via @tidbit. > > Note that such session vars can survive app restarts. So if you > really want the var to be set at app start/restart, and/or you change > the structure/content of tidbit in the db, you'll want to clear such > session data first before re-starting your app. > > If var that you're setting really is global in scope, intended to be > shared by all users' requests and is read-only, then you could store > it in a global var: > > # in ./app/controller/application.rb > ... > before_filter :do_lazy_init > > ... > private > > def do_lazy_init > $global_tidbit = Tidbit.random if not $global_tidbit > @tidbit = $global_tidbit > end > > Beware of issues surrounding use of global vars tho, and definitely > don't use mutable global vars, due to potential data incongruity > issues, especially when running production environment (assuming more > than one process-/thread-instance of your app in prod env). > > If you're interested in Matz's opinion on use of global vars, per > quote in Ruby Pocket Ref (http://books.google.com/books? > id=KZU_HUYJ5yMC&pg=PA13&dq=ruby+matz+global+variables): "They're ugly, > so don't use them." > > Jeff > > On Feb 21, 4:29 pm,ericindc wrote: > > > I don't generally follow the "whatever works..." approach because > > there is usually a best practice. That said, I want to avoid the > > global variable because having $tidbit = Tidbit.random declared in my > > application.rb broke my migrations. Running migrations from version 0 > > when the Tidbits database doesn't exist caused the db:migrate to fail > > because the line of code was still being executed and the Model was > > attempting to access a table that didn't exist. > > > I'll keep reading, but I'm sure there is a logical way of > > accomplishing this that I'm just not yet seeing. Thanks. > > > On Feb 21, 4:41 pm, Eric wrote: > > > > So why not use that, then? Whatever works... > > > > Also, you might brush up on MVC and beginner's Ruby as far as "setting > > > variables in models" > > > go:http://wiki.rubyonrails.org/rails/pages/UnderstandingRailsMVC > > > > On Feb 21, 12:45 pm,ericindc wrote: > > > > > Title pretty much explains it. I'd like to set a variable the stores > > > > a single Model object inside of application.rb since it will be used > > > > on every single page. I've tried both class and instance variables, > > > > but to no avail. The only thing that worked so far was using a global > > > > ($) variable. > > --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~--~~~~--~~--~--~---
[Rails] Re: How do I access a variable defined in application.rb from within application.rhtml?
hi, Ruby pocket reference looks useful, think I'll order a copy. Regarding the class method, just wondering when/how this method should get called. Tonypm --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~--~~~~--~~--~--~---
[Rails] Re: How do I access a variable defined in application.rb from within application.rhtml?
For actual read-only data that is an instance of a model class, I'd
set up a class method instead. So for a default location, in
Location.rb,
def self.default_location
@@default_location ||= Location.find_by_name("San Francisco")
end
This fixes your migration problem, doesn't reload it with every page,
and also works with testing.
On Sun, Feb 22, 2009 at 4:24 PM, Jeff Lewis wrote:
[...]
> If var that you're setting really is global in scope, intended to be
> shared by all users' requests and is read-only, then you could store
> it in a global var:
[...]
--~--~-~--~~~---~--~~
You received this message because you are subscribed to the Google Groups "Ruby
on Rails: Talk" group.
To post to this group, send email to rubyonrails-talk@googlegroups.com
To unsubscribe from this group, send email to
rubyonrails-talk+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~--~~~~--~~--~--~---
[Rails] Re: How do I access a variable defined in application.rb from within application.rhtml?
To initialize some db-read var (tidbit in your example) that would survive and be callable for each subsequent app request, you'll want to do so via lazy-initialization using a before_filter (mentioned by bill) in application.rb. How you store such lazy-init vars between requests depends on the scope/use of such vars by users/requests of the app: If the var that you're setting is specific to some user alone, and should not be shared by all users' requests, then you could store that var in the user's session: # in ./app/controller/application.rb ... before_filter :do_lazy_init ... private def do_lazy_init session[:tidbit] = Tidbit.random if not session[:tidbit] @tidbit = session[:tidbit] end which all of your app controller meths and view templates could then use via @tidbit. Note that such session vars can survive app restarts. So if you really want the var to be set at app start/restart, and/or you change the structure/content of tidbit in the db, you'll want to clear such session data first before re-starting your app. If var that you're setting really is global in scope, intended to be shared by all users' requests and is read-only, then you could store it in a global var: # in ./app/controller/application.rb ... before_filter :do_lazy_init ... private def do_lazy_init $global_tidbit = Tidbit.random if not $global_tidbit @tidbit = $global_tidbit end Beware of issues surrounding use of global vars tho, and definitely don't use mutable global vars, due to potential data incongruity issues, especially when running production environment (assuming more than one process-/thread-instance of your app in prod env). If you're interested in Matz's opinion on use of global vars, per quote in Ruby Pocket Ref (http://books.google.com/books? id=KZU_HUYJ5yMC&pg=PA13&dq=ruby+matz+global+variables): "They're ugly, so don't use them." Jeff On Feb 21, 4:29 pm, ericindc wrote: > I don't generally follow the "whatever works..." approach because > there is usually a best practice. That said, I want to avoid the > global variable because having $tidbit = Tidbit.random declared in my > application.rb broke my migrations. Running migrations from version 0 > when the Tidbits database doesn't exist caused the db:migrate to fail > because the line of code was still being executed and the Model was > attempting to access a table that didn't exist. > > I'll keep reading, but I'm sure there is a logical way of > accomplishing this that I'm just not yet seeing. Thanks. > > On Feb 21, 4:41 pm, Eric wrote: > > > So why not use that, then? Whatever works... > > > Also, you might brush up on MVC and beginner's Ruby as far as "setting > > variables in models" > > go:http://wiki.rubyonrails.org/rails/pages/UnderstandingRailsMVC > > > On Feb 21, 12:45 pm, ericindc wrote: > > > > Title pretty much explains it. I'd like to set a variable the stores > > > a single Model object inside of application.rb since it will be used > > > on every single page. I've tried both class and instance variables, > > > but to no avail. The only thing that worked so far was using a global > > > ($) variable. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~--~~~~--~~--~--~---
[Rails] Re: How do I access a variable defined in application.rb from within application.rhtml?
Hi Eric, On Sat, 2009-02-21 at 12:45 -0800, ericindc wrote: > Title pretty much explains it. I'd like to set a variable the stores > a single Model object inside of application.rb since it will be used > on every single page. I've tried both class and instance variables, > but to no avail. The only thing that worked so far was using a global > ($) variable. It sounds like, maybe you're setting it once in application.rb rather than once per request/response cycle? Instance variables (and IIRC class variables too) have a one-cycle lifetime. That would explain why a global 'works'. The 'typical' approach to setting an instance variable that's needed for every render would be to add a before_filter in all your controllers that invokes the application.rb method. HTH, Bill --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~--~~~~--~~--~--~---
[Rails] Re: How do I access a variable defined in application.rb from within application.rhtml?
I don't generally follow the "whatever works..." approach because there is usually a best practice. That said, I want to avoid the global variable because having $tidbit = Tidbit.random declared in my application.rb broke my migrations. Running migrations from version 0 when the Tidbits database doesn't exist caused the db:migrate to fail because the line of code was still being executed and the Model was attempting to access a table that didn't exist. I'll keep reading, but I'm sure there is a logical way of accomplishing this that I'm just not yet seeing. Thanks. On Feb 21, 4:41 pm, Eric wrote: > So why not use that, then? Whatever works... > > Also, you might brush up on MVC and beginner's Ruby as far as "setting > variables in models" > go:http://wiki.rubyonrails.org/rails/pages/UnderstandingRailsMVC > > On Feb 21, 12:45 pm, ericindc wrote: > > > Title pretty much explains it. I'd like to set a variable the stores > > a single Model object inside of application.rb since it will be used > > on every single page. I've tried both class and instance variables, > > but to no avail. The only thing that worked so far was using a global > > ($) variable. > > --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~--~~~~--~~--~--~---
[Rails] Re: How do I access a variable defined in application.rb from within application.rhtml?
So why not use that, then? Whatever works... Also, you might brush up on MVC and beginner's Ruby as far as "setting variables in models" go: http://wiki.rubyonrails.org/rails/pages/UnderstandingRailsMVC On Feb 21, 12:45 pm, ericindc wrote: > Title pretty much explains it. I'd like to set a variable the stores > a single Model object inside of application.rb since it will be used > on every single page. I've tried both class and instance variables, > but to no avail. The only thing that worked so far was using a global > ($) variable. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~--~~~~--~~--~--~---
