In this section we'll finally learn key feature of Move - resources. They are what makes Move unique, safe and powerful.
To start, let's go through key points from libra developers website:
- The key feature of Move is the ability to define custom resource types. Resource types are used to encode safe digital assets with rich programmability.
- Resources are ordinary values in the language. They can be stored as data structures, passed as arguments to procedures, returned from procedures, and so on.
Resource is a special type of structure, and it is possible to define and create new (or use existing) resource right in the Move code. Therefore you're able to manage digital assets the same way you use any other data (like vector or struct).
- The Move type system provides special safety guarantees for resources. Move resources can never be duplicated, reused, or discarded. A resource type can only be created or destroyed by the module that defines the type. These guarantees are enforced statically by the Move virtual machine via bytecode verification. The Move virtual machine will refuse to run code that has not passed through the bytecode verifier.
In references and ownership chapter you've seen how Move secures scopes and controls variable's owner scope. And in generics chapter you've learned that there's a special way of kind-matching to separate copyable and non-copyable types. All of these features provide safety for resource type.
- All Libra currencies are implemented using the generic Libra::T type. For example: the LBR currency is represented as Libra::TLBR::T and a hypothetical USD currency would be represented as Libra::TUSD::T. Libra::T has no special status in the language; every Move resource enjoys the same protections.
Just like the Libra currency, other currencies or other types of assets can be represented in Move.