signal

concepts Holochain

• Don’t wait for a response: fire and forget
• Not reliable: signals can be lost without our code knowing
• 2 types: 
  • Remote Signals
    • Concurrent call to multiple agents
    • Very similar to “call_remote”
    • Useful for notifications
  • UI Signals
    • Send message from the conductor to all processes that are listening

Remote signals

use hdk::prelude::*;
 
#[hdk_extern]
fn notify(agents_to_notify: Vec<AgentPubkey>) -> ExternResult<()> { 
  let input_string = String::from("input parameter");
 
  let input = ExternIO::encode(input_string)?; // Wrapping input 
 
  remote_signal(input, agents_to_notify)?; // Doesn't wait 
 
  Ok(())
}

UI signals

use hdk::prelude::*;
 
#[hdk_extern]
fn notify_ui(_: ()) -> ExternResult<()> { 
let input_string = String::from("input parameter");
 
  emit_signal(input_string)?; // Notify all processes connected to the conductor 
 
  Ok(())
}