In considering AI use cases and capabilities, I set Claude.ai on the task of describing the life cycle and events for PhoenixLiveView LiveComponent. The prompt, including my typo:

Draw a collection of sequence diagrams to explain event handling and callbacks for PhoenixLiveView LiveComponents work (documentation is https://hexdocs.pm/phoenix_live_view/Phoenix.LiveComponent.html#callbacks) written as mermaid code (reference documentation is https://mermaid.js.org/syntax/sequenceDiagram.html).

The high level output was:

I’ll create a collection of sequence diagrams that explain event handling and callbacks for Phoenix LiveView LiveComponents using Mermaid. These diagrams will help visualize the lifecycle and interactions of LiveComponents.

Phoenix LiveComponent Sequence DiagramsDiagram 

Let me create a few more diagrams to cover different aspects of LiveComponent interactions:

  1. LiveComponent Event HandlingDiagram 
  2. LiveComponent Message HandlingDiagram 
  3. LiveComponent Parent-Child CommunicationDiagram 
  4. Stateful LiveComponent LifecycleDiagram 

These sequence diagrams illustrate the key interactions and lifecycle of Phoenix LiveComponents:

Initial Mount: Shows how a LiveComponent is initialized and rendered during the first page load.

Event Handling: Demonstrates how events are processed, differentiating between events targeted directly at the component versus those handled by the parent LiveView.

Message Handling: Illustrates how send_update works to trigger out-of-band updates to components.

Parent-Child Communication: Shows the two primary ways parent LiveViews communicate with child LiveComponents.

Stateful Component Lifecycle: Details how stateful LiveComponents maintain their state across multiple interactions.

Each diagram visualizes different aspects of the LiveComponent lifecycle, helping to clarify how these components interact with LiveViews and the browser. Would you like me to explain any specific aspect of these diagrams in more detail?

The diagrams are below. I’ve looked at them for a few minutes and compared them with the documentation. They seem correct, although I may have missed an error. If you find a mistake or something significantly missing, please let me know ( dan-janowski).

These strike me as pretty well formed and useful diagrams. It would have taken me more than an hour, probably a few, to decide which diagrams to make and the contents. Writing this article has already taken significantly longer to write than Claude took to generate the diagrams. Though I did write updated mermaid and link generating plugins for Liquid to make this post.

LiveComponent Lifecycle - Initial Mount

sequenceDiagram title LiveComponent Lifecycle - Initial Mount Browser->>LiveView: Initial Request LiveView->>LiveComponent: mount/1 Note over LiveComponent: Initialize state LiveComponent->>LiveView: Return socket LiveView->>LiveComponent: update/2 Note over LiveComponent: Process assigns LiveComponent->>LiveView: Return updated socket LiveView->>LiveComponent: render/1 Note over LiveComponent: Generate HTML LiveComponent->>LiveView: Return rendered HTML LiveView->>Browser: Send HTML response

LiveComponent Event Handling

sequenceDiagram title LiveComponent Event Handling Browser->>LiveView: User Event (phx-click, etc.) Note over LiveView: Event contains phx-target alt Event Targeted at LiveComponent LiveView->>LiveComponent: handle_event/3 Note over LiveComponent: Process event LiveComponent->>LiveComponent: Update internal state LiveComponent->>LiveView: Return updated socket LiveView->>LiveComponent: render/1 LiveComponent->>LiveView: Return rendered HTML LiveView->>Browser: Send HTML diff else Event Targeted at Parent LiveView LiveView->>LiveView: handle_event/3 Note over LiveView: Process event LiveView->>LiveView: Update state LiveView->>LiveComponent: update/2 (if state affects component) LiveComponent->>LiveView: Return updated socket LiveView->>LiveComponent: render/1 LiveComponent->>LiveView: Return rendered HTML LiveView->>Browser: Send HTML diff end

LiveComponent Message Handling (send_update)

sequenceDiagram title LiveComponent Message Handling (send_update) participant Process as "External Process" participant LVReg as "LiveView Registry" participant LiveView participant LiveComponent Process->>LVReg: send_update(Component, id: id, ...) LVReg->>LiveView: Find LiveView containing component LiveView->>LiveComponent: update/2 Note over LiveComponent: Process updated assigns LiveComponent->>LiveView: Return updated socket LiveView->>LiveComponent: render/1 LiveComponent->>LiveView: Return rendered HTML LiveView->>Browser: Send HTML diff

LiveComponent Parent-Child Communication

sequenceDiagram title LiveComponent Parent-Child Communication Browser->>LiveView: User Event LiveView->>LiveView: handle_event/3 Note over LiveView: Update state alt Using assign LiveView->>LiveComponent: update/2 with new assigns LiveComponent->>LiveView: Return updated socket else Using send_update LiveView->>LiveComponent: Phoenix.LiveView.send_update Note over LiveComponent: Component receives out-of-band update LiveComponent->>LiveView: Trigger re-render end LiveView->>LiveComponent: render/1 LiveComponent->>LiveView: Return rendered HTML LiveView->>Browser: Send HTML diff

Stateful LiveComponent Lifecycle

sequenceDiagram title Stateful LiveComponent Lifecycle Browser->>LiveView: Initial Request LiveView->>LiveComponent: mount/1 Note over LiveComponent: Initialize state in socket LiveComponent->>LiveView: Return socket with state Browser->>LiveView: User Event (phx-target=component) LiveView->>LiveComponent: handle_event/3 Note over LiveComponent: Process event with socket state LiveComponent->>LiveComponent: Update socket state LiveComponent->>LiveView: Return updated socket LiveView->>Browser: Send HTML diff Note over LiveComponent: State persists between renders Browser->>LiveView: Another User Event LiveView->>LiveComponent: handle_event/3 Note over LiveComponent: Access previous state from socket LiveComponent->>LiveView: Return updated socket LiveView->>Browser: Send HTML diff