generic_singleton
Rust does NOT monomorphize it's static generic items. This means you cannot use a generic static item in a generic function. You'll get the following error:
error[E0401]: can't use generic parameters from outer function
That's pretty frustrating when you want to write a singleton pattern that rely's on a generic parameter. This crate allows for this pattern with minimal runtime overhead.
generic_singleton
uses anymap behind the scenes to store a map of each
generic type. The first time you hit the get_or_init
macro we initialize the
singleton. Subsequent calls to get_or_init
will retrieve the singleton from
the map.
Example
use ;
use ;
Thread Local variant
The example shown above has a drawback of requiring an RwLock
to ensure
synchronisation around the inner AnyMap. In single-threaded situations we can
remove this lock and provide mutable references directly using the
get_or_init_thread_local!
macro. This comes at the cost of ergonomics,
requiring you to express your logic in a closure rather than simply returning a
reference.