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Ottorino Bruni  

How to Modify Variable Values in Xcode Debugger

Let’s face it, having a bunch of solid tests is usually the best way to keep your code in check. But, there are those moments when you just need to peek at and mess around with variable values while your code is doing its thing. Sure, we all know Xcode is our go-to for fixing bugs, but did you know there are some cool and simple tricks to mess with variable values? In this article, we’re diving into the nitty-gritty of tweaking variables on the fly in Xcode.

Certainly! If you’re coming from the Visual Studio world, you might notice the absence of something like the “Immediate Window” in Xcode. While Visual Studio offers a tool called the “Immediate Window” for executing commands during debugging and instantly seeing the results, Xcode primarily uses the debug console for similar purposes.

LLDB: The Debugging Wizard

LLDB is the default debugger in Xcode on macOS and supports debugging C, Objective-C and C++ on the desktop and iOS devices/simulator and it plays a crucial role in inspecting and manipulating the inner workings of our code during runtime.

Changing Variables in Xcode Console

When our app pauses at a breakpoint, the Xcode console becomes the place where we can easily tweak variable values. In the image below, you’ll see our trusty debugger in action. When it comes to checking variable values, we rely on the po command, shorthand for “print object,” to easily display the current value. On the flip side, the expression command (or expr for short) steals the spotlight when we’re in the mood to switch things up and modify a variable on the fly.

How to Modify Variable Values in Xcode Debugger

For a comprehensive list of expressions, head over to LLDB Evaluating Expressions.

Modify a value during iOS debugging in Xcode

Be Aware: Potential Challenges When Modifying Variables

While the ability to tweak variables on the fly in Xcode can be a game-changer for debugging, it comes with its own set of challenges. Here are some key points to keep in mind:

  1. Be aware of variable scope.
  2. Don’t forget to reset values.
  3. Explore watchpoints as an alternative.

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