Debugging a form that does not update correctly within an Elixir LiveView component can be approached by checking multiple aspects of your code. Below are steps to guide you through the debugging process:
Check the HTML Form Structure:
Ensure that the form tag includes the phx-submit attribute with the correct event name.
Make sure that input fields have the phx-change attribute if you want to handle changes live.
Each input should have a name attribute that corresponds to the field in your changeset or assigns.
Inspect the Changeset:
Verify your changeset function in the LiveView is defined correctly and is returning a properly structured changeset with the fields you expect to change.
Ensure that the changeset function is called with the appropriate parameters upon form submission or changes.
Review LiveView Event Handlers:
Review the functions that handle the phx-submit, phx-change, phx-click, etc., events. Make sure they are correctly defined and named as referenced in the form's template.
Ensure that you're correctly pattern-matching on the events and handling them properly.
Check Assigns Management:
Look at how assigns are being managed in the socket. Make sure that you're updating assigns when changes to form fields are made.
Make sure that the assigns used by the form are not being inadvertently modified somewhere else in the LiveView.
Look for JavaScript Interferences:
Sometimes, JavaScript that's running on the client side could interfere with the LiveView hooks or form submission. Disable any other JavaScript on the page and check if the problem persists.
Check the LiveView Lifecycle:
Ensure the mount/3, handle_params/3, render/1, or other lifecycle callbacks are not causing conflicts or resetting the form state inadvertently.
Utilize Logger:
Use Logger.debug/2 to print out the internal state of your LiveView whenever an event is handled. This can help you understand what happens before and after a form event.
Examine Network Traffic:
Open your browser's developer tools and inspect the WebSocket frames to see what is being transmitted between client and server. You should see events being sent to the server and diffs coming back to the client.
Verify Database Operations:
If the form submission involves database operations (like inserts or updates), check if those operations are successful and not raising any exceptions.
Testing:
Write tests for your LiveView using tools like Phoenix.LiveViewTest. This can help you isolate and reproduce the issue in a controlled environment.
Debugging Tools:
Use IO.inspect/2, require IEx; IEx.pry, raise/1, or the :debugger module from Erlang to insert breakpoints and step through your code if you're running in a development environment.
As you debug, keep in mind the real-time aspect of LiveView, which means that any server-side errors are likely to be shown in the server logs rather than the browser console. Regularly check the console where your Phoenix server is running to spot any error messages or logs.
Once you've looked through these areas, if your form is still not updating correctly, you may need to investigate for more subtle bugs or edge cases specific to your application's logic or the state management of your LiveView component.
Debugging a form that does not update correctly within an Elixir LiveView component can be approached by checking multiple aspects of your code. Below are steps to guide you through the debugging process:
Check the HTML Form Structure:
phx-submitattribute with the correct event name.phx-changeattribute if you want to handle changes live.nameattribute that corresponds to the field in your changeset or assigns.Inspect the Changeset:
Review LiveView Event Handlers:
phx-submit,phx-change,phx-click, etc., events. Make sure they are correctly defined and named as referenced in the form's template.Check Assigns Management:
Look for JavaScript Interferences:
Check the LiveView Lifecycle:
mount/3,handle_params/3,render/1, or other lifecycle callbacks are not causing conflicts or resetting the form state inadvertently.Utilize Logger:
Logger.debug/2to print out the internal state of your LiveView whenever an event is handled. This can help you understand what happens before and after a form event.Examine Network Traffic:
Verify Database Operations:
Testing:
Phoenix.LiveViewTest. This can help you isolate and reproduce the issue in a controlled environment.Debugging Tools:
IO.inspect/2,require IEx; IEx.pry,raise/1, or the:debuggermodule from Erlang to insert breakpoints and step through your code if you're running in a development environment.As you debug, keep in mind the real-time aspect of LiveView, which means that any server-side errors are likely to be shown in the server logs rather than the browser console. Regularly check the console where your Phoenix server is running to spot any error messages or logs.
Once you've looked through these areas, if your form is still not updating correctly, you may need to investigate for more subtle bugs or edge cases specific to your application's logic or the state management of your LiveView component.
created by ross.garfield@revelry.co using Prodops