When it comes to swift app development, debugging is a crucial step in identifying and resolving issues within your code. In this article, we'll explore how to use Xcode's built-in debugger to streamline your development process.

Getting Started with the Debugger

Xcode provides a comprehensive source-level debugger that supports breakpoints, stepping, and variable inspection. To access the debugger, navigate to the DevTools tab in your Xcode project. You should see the main entry-point for your app loaded in the debugger area. From here, you can browse other source files by clicking the "Libraries" button or pressing Ctrl/Cmd + P.

Setting Breakpoints

To set a breakpoint, click on the left margin (the line number ruler) in the source area. Clicking once sets a breakpoint, which will also appear in the Breakpoints area on the left. Clicking again removes the breakpoint. With breakpoints in place, you can pause your app's execution and inspect the current state of your code.

Exploring the Debugger Interface

When your application encounters a breakpoint, it pauses execution at that point, and the DevTools debugger shows the paused execution location in the source area. The Call stack and Variables areas will also populate with the current call stack for the paused isolate and the local variables for the selected frame. By selecting other frames in the Call stack area, you can change the contents of the variables.

Within the Variables area, you can inspect individual objects by toggling them open to see their fields. Hovering over an object in the Variables area will display the result of calling toString() on that object.

Stepping Through Source Code

When paused, the three stepping buttons become active:

  • Step into: Steps into a method invocation, stopping at the first executable line in that invoked method.
  • Step over: Steps over a method invocation, this steps through source lines in the current method.
  • Step out: Steps out of the current method without stopping at any intermediary lines.

Additionally, the Resume button continues regular execution of your app.

Monitoring Console Output

Console output for your running app (stdout and stderr) is displayed in the console area below the source code. You can also view the output in the Logging view.

Breaking on Exceptions

To adjust the stop-on-exceptions behavior, toggle the Ignore dropdown at the top of the debugger view. This allows you to customize when your app pauses execution due to exceptions. For example, breaking on unhandled exceptions will only pause execution if the breakpoint is considered uncaught by your application code.

Troubleshooting and Additional Resources

When performing a hot restart for a Flutter application, user breakpoints are cleared. For more information on debugging and profiling, see the Debugging page.