update

src/client/async.rs

@@ -614,6 +614,40 @@ impl Client {
         display_groups::r#async::subscribe_to_group_events(self, group_id).await
     }
 
+    /// Updates the contract displayed in a TWS display group.
+    ///
+    /// This function changes the contract shown in the specified display group within TWS.
+    /// You must first subscribe to the group using [`subscribe_to_group_events`](Self::subscribe_to_group_events)
+    /// before calling this function.
+    ///
+    /// # Arguments
+    /// * `request_id` - The request ID from the subscription (use `subscription.request_id()`)
+    /// * `contract_info` - Contract to display:
+    ///   - `"contractID@exchange"` for individual contracts (e.g., "265598@SMART")
+    ///   - `"none"` for empty selection
+    ///   - `"combo"` for combination contracts
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use ibapi::Client;
+    ///
+    /// #[tokio::main]
+    /// async fn main() {
+    ///     let client = Client::connect("127.0.0.1:7497", 100).await.expect("connection failed");
+    ///
+    ///     // First subscribe to the display group
+    ///     let subscription = client.subscribe_to_group_events(1).await.expect("subscription failed");
+    ///     let request_id = subscription.request_id().expect("no request ID");
+    ///
+    ///     // Update the display group to show AAPL
+    ///     client.update_display_group(request_id, "265598@SMART").await.expect("update failed");
+    /// }
+    /// ```
+    pub async fn update_display_group(&self, request_id: i32, contract_info: &str) -> Result<(), Error> {
+        display_groups::r#async::update_display_group(self, request_id, contract_info).await
+    }
+
     // === Market Data ===
 
     /// Creates a market data subscription builder with a fluent interface.

src/client/sync.rs

@@ -520,6 +520,37 @@ impl Client {
         display_groups::sync::subscribe_to_group_events(self, group_id)
     }
 
+    /// Updates the contract displayed in a TWS display group.
+    ///
+    /// This function changes the contract shown in the specified display group within TWS.
+    /// You must first subscribe to the group using [`subscribe_to_group_events`](Self::subscribe_to_group_events)
+    /// before calling this function.
+    ///
+    /// # Arguments
+    /// * `request_id` - The request ID from the subscription (use `subscription.request_id()`)
+    /// * `contract_info` - Contract to display:
+    ///   - `"contractID@exchange"` for individual contracts (e.g., "265598@SMART")
+    ///   - `"none"` for empty selection
+    ///   - `"combo"` for combination contracts
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use ibapi::client::blocking::Client;
+    ///
+    /// let client = Client::connect("127.0.0.1:7497", 100).expect("connection failed");
+    ///
+    /// // First subscribe to the display group
+    /// let subscription = client.subscribe_to_group_events(1).expect("subscription failed");
+    /// let request_id = subscription.request_id().expect("no request ID");
+    ///
+    /// // Update the display group to show AAPL
+    /// client.update_display_group(request_id, "265598@SMART").expect("update failed");
+    /// ```
+    pub fn update_display_group(&self, request_id: i32, contract_info: &str) -> Result<(), Error> {
+        display_groups::sync::update_display_group(self, request_id, contract_info)
+    }
+
     // === Contracts ===
 
     /// Requests contract information.

src/display_groups/async.rs

@@ -22,6 +22,25 @@ pub async fn subscribe_to_group_events(client: &Client, group_id: i32) -> Result
     builder.send::<DisplayGroupUpdate>(request).await
 }
 
+/// Updates the contract displayed in a TWS display group.
+///
+/// This function changes the contract shown in the specified display group within TWS.
+/// You must first subscribe to the group using [`subscribe_to_group_events`] before
+/// calling this function. The update will trigger a `DisplayGroupUpdated` callback
+/// on the existing subscription.
+///
+/// # Arguments
+/// * `client` - The connected client
+/// * `request_id` - The request ID from the subscription (use `subscription.request_id()`)
+/// * `contract_info` - Contract to display:
+///   - `"contractID@exchange"` for individual contracts (e.g., "265598@SMART")
+///   - `"none"` for empty selection
+///   - `"combo"` for combination contracts
+pub async fn update_display_group(client: &Client, request_id: i32, contract_info: &str) -> Result<(), Error> {
+    let request = encoders::encode_update_display_group(request_id, contract_info)?;
+    client.send_message(request).await
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

src/display_groups/common/encoders.rs

@@ -24,6 +24,21 @@ pub(crate) fn encode_unsubscribe_from_group_events(request_id: i32) -> Result<Re
     Ok(message)
 }
 
+/// Encodes a request to update the contract displayed in a display group.
+///
+/// # Arguments
+/// * `request_id` - The request ID (should match the subscription request ID)
+/// * `contract_info` - Contract to display, format: "contractID@exchange" (e.g., "265598@SMART"),
+///   "none" for empty selection, or "combo" for combination contracts
+pub(crate) fn encode_update_display_group(request_id: i32, contract_info: &str) -> Result<RequestMessage, Error> {
+    let mut message = RequestMessage::new();
+    message.push_field(&OutgoingMessages::UpdateDisplayGroup);
+    message.push_field(&VERSION);
+    message.push_field(&request_id);
+    message.push_field(&contract_info);
+    Ok(message)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -52,4 +67,28 @@ mod tests {
         assert_eq!(message[1], "1"); // version
         assert_eq!(message[2], request_id.to_field());
     }
+
+    #[test]
+    fn test_encode_update_display_group() {
+        let request_id = 9000;
+        let contract_info = "265598@SMART";
+
+        let message = encode_update_display_group(request_id, contract_info).expect("encoding failed");
+
+        assert_eq!(message[0], OutgoingMessages::UpdateDisplayGroup.to_field());
+        assert_eq!(message[1], "1"); // version
+        assert_eq!(message[2], request_id.to_field());
+        assert_eq!(message[3], contract_info);
+    }
+
+    #[test]
+    fn test_encode_update_display_group_none() {
+        let request_id = 9000;
+        let contract_info = "none";
+
+        let message = encode_update_display_group(request_id, contract_info).expect("encoding failed");
+
+        assert_eq!(message[0], OutgoingMessages::UpdateDisplayGroup.to_field());
+        assert_eq!(message[3], "none");
+    }
 }

src/display_groups/sync.rs

@@ -21,3 +21,22 @@ pub fn subscribe_to_group_events(client: &Client, group_id: i32) -> Result<Subsc
     let request = encoders::encode_subscribe_to_group_events(builder.request_id(), group_id)?;
     builder.send(request)
 }
+
+/// Updates the contract displayed in a TWS display group.
+///
+/// This function changes the contract shown in the specified display group within TWS.
+/// You must first subscribe to the group using [`subscribe_to_group_events`] before
+/// calling this function. The update will trigger a `DisplayGroupUpdated` callback
+/// on the existing subscription.
+///
+/// # Arguments
+/// * `client` - The connected client
+/// * `request_id` - The request ID from the subscription (use `subscription.request_id()`)
+/// * `contract_info` - Contract to display:
+///   - `"contractID@exchange"` for individual contracts (e.g., "265598@SMART")
+///   - `"none"` for empty selection
+///   - `"combo"` for combination contracts
+pub fn update_display_group(client: &Client, request_id: i32, contract_info: &str) -> Result<(), Error> {
+    let request = encoders::encode_update_display_group(request_id, contract_info)?;
+    client.send_message(request)
+}

src/subscriptions/async.rs

@@ -227,6 +227,11 @@ impl<T> Subscription<T> {
             SubscriptionInner::PreDecoded { receiver } => receiver.recv().await,
         }
     }
+
+    /// Get the request ID associated with this subscription
+    pub fn request_id(&self) -> Option<i32> {
+        self.request_id
+    }
 }
 
 impl<T> Subscription<T> {

src/subscriptions/sync.rs

@@ -95,6 +95,11 @@ impl<T: StreamDecoder<T>> Subscription<T> {
         }
     }
 
+    /// Returns the request ID associated with this subscription.
+    pub fn request_id(&self) -> Option<i32> {
+        self.request_id
+    }
+
     /// Returns the next available value, blocking if necessary until a value becomes available.
     ///
     /// # Examples