This blog is part of our Rails 5 series.
Rails already provides methods for creating class level and module level variables in the form of cattr_* and mattr_* suite of methods.
In Rails 5, we can go a step further and create thread specific class or module level variables.
Here is an example which demonstrates an example on how to use it.
CurrentScope.user_permissions will be available till the lifetime of
currently executing thread and all the code after this point
can use this variable.
For example, we can access this variable in any of the models
without explicitly passing
current_user from the controller.
It internally uses Thread.current#= method,
so all the variables are scoped to the thread currently executing.
It will also take care of namespacing these variables per class or module
RequestScope.user_permissions will not conflict
with each other.
If you have used PerThreadRegistry before for managing global variables,
thread_cattr_* methods can be used in place of it starting from Rails 5.
Globals are generally bad and should be avoided but this change provides nicer API if you want to fiddle with them anyway!