Examples of how to use ink! Rust in smart contract. The work has already been done for a while, and released to the community. 
https://github.com/polblancoo/Curso-Ink
Thanks

amount

beneficiary

Rejected

Submitted

DecisionStarted

DecisionDepositPlaced

small_tipper

Rust, ink! technical content for  developers

root

whitelisted_caller

wish_for_change

staking_admin

treasurer

lease_admin

fellowship_admin

general_admin

auction_admin

referendum_canceller

referendum_killer

big_tipper

small_spender

medium_spender

big_spender

Origin able to dispatch a whitelisted call.

Origin for signaling that the network wishes for some change

Origin able to cancel slashes and manage minimum commission.

Origin for spending up to 10,000,000 DOT from the treasury as well as generally administering it.

Origin for managing the composition of the fellowship.

Origin able to spend around 250 DOT from the treasury at once.

Origin able to spend around 1,000 DOT from the treasury at once.

Origin able to spend around 10,000 DOT from the treasury at once.

Origin able to spend around 100,000 DOT from the treasury at once.

Origin able to spend up to 1,000,000 DOT from the treasury at once.