Use the Debug console

The DevTools Debug console allows you to watch an application's standard output (stdout), evaluate expressions for a paused or running app in debug mode, and analyze inbound and outbound references for objects.

The Debug console is available from the Inspector, Debugger, and Memory views.

Watch application output


The console shows the application's standard output (stdout):

Screenshot of stdout in Console view

Explore inspected widgets


If you click a widget on the Inspector screen, the variable for this widget displays in the Console:

Screenshot of inspected widget in Console view

Evaluate expressions


In the console, you can evaluate expressions for a paused or running application, assuming that you are running your app in debug mode:

Screenshot showing evaluating an expression in the console

To assign an evaluated object to a variable, use $0, $1 (through $5) in the form of var x = $0:

Screenshot showing how to evaluate variables

Browse heap snapshot


To drop a variable to the console from a heap snapshot, do the following:

  1. Navigate to Devtools > Memory > Diff Snapshots.
  2. Record a memory heap snapshot.
  3. Click on the context menu [⋮] to view the number of Instances for the desired Class.
  4. Select whether you want to store a single instance as a console variable, or whether you want to store all currently alive instances in the app.

Screenshot showing how to browse the heap snapshots

The Console screen displays both live and static inbound and outbound references, as well as field values:

Screenshot showing inbound and outbound references in Console