Access control

// Ownable has to be imported from stdlib, as well as Deployable, for convenience:
import "@stdlib/ownable";
import "@stdlib/deploy";
 
message FooBarMsg {
    newVal: Int as uint32;
}
 
// Ownable trait can limit certain actions to the owner only
contract SenderChecker with Deployable, Ownable {
    // Persistent state variables
    owner: Address;     // Ownable trait requires you to add this exact state variable
    val: Int as uint32; // some value
 
    init() {
        // we can initialize owner to any value we want, the deployer in this case:
        self.owner = sender();
        self.val = 0;
    }
 
    receive("inc") {
        require(self.owner == sender(), "Only the owner can increase the value!");
        self.val += 1;
    }
 
    receive(msg: FooBarMsg) {
        require(self.owner == sender(), "Only the owner can set the value!");
        self.val = msg.newVal;
    }
}