Return Result:Err instead of asserting

examples/proxy/lib.rs

@@ -31,6 +31,25 @@ pub mod proxy {
         admin: AccountId,
     }
 
+    /// Error which is returned if a caller tries to invoke
+    /// [`Proxy::change_forward_address`] while not being the
+    /// admin account stored in the storage of this contract.
+    #[derive(scale::Encode, scale::Decode)]
+    #[cfg_attr(feature = "std", derive(scale_info::TypeInfo))]
+    pub struct NotAdminErr {
+        admin: AccountId,
+    }
+
+    impl core::fmt::Display for NotAdminErr {
+        fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
+            let msg = format!(
+                "caller does not have sufficient permissions, only {:?} does",
+                self.admin
+            );
+            write!(f, "{}", msg)
+        }
+    }
+
     impl Proxy {
         /// Instantiate this contract with an address of the `logic` contract.
         ///
@@ -46,16 +65,25 @@ pub mod proxy {
 
         /// Changes the `AccountId` of the contract where any call that does
         /// not match a selector of this contract is forwarded to.
+        ///
+        /// Returns a [`NotAdminErr`] in case the caller is not the
+        /// admin account stored in the storage of this contract.
+        ///
+        /// # Note:
+        ///
+        /// Returning an `Result::Err` here will result in the transaction
+        /// being reverted, in that sense it is equal to e.g. placing an
+        /// `assert!` here instead.
         #[ink(message)]
-        pub fn change_forward_address(&mut self, new_address: AccountId) {
-            assert_eq!(
-                self.env().caller(),
-                self.admin,
-                "caller {:?} does not have sufficient permissions, only {:?} does",
-                self.env().caller(),
-                self.admin,
-            );
+        pub fn change_forward_address(
+            &mut self,
+            new_address: AccountId,
+        ) -> Result<(), NotAdminErr> {
+            if self.env().caller() != self.admin {
+                return Err(NotAdminErr { admin: self.admin })
+            }
             self.forward_to = new_address;
+            Ok(())
         }
 
         /// Fallback message for a contract call that doesn't match any