Bilal Arslan
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Language: English

Xcode Debugging Tips

Changing interface properties during a debugging session, without rebuilding your app.

From the archive: first published in 2017. The tools and features described reflect that time.

Xcode debugging is a handy feature while coding. In the number of the Xcode debugging features, there is a useful one I have recently discovered to use effectively.

As we know, we can easily print all variables in the debugging session variable list.

For example:

po anArray
po aString
po evenViewObjects

As I write in the examples, we can print all kinds of view objects inherited from UIView objects. What if we should change the property of a view object? For example text of UILabel.

Let’s look at what we should write for this. You can download the basic project here to test yourself.

Here is the initial screen of the app, we are going to change the text property of the label(aLabel) and the backgroundColor property of the button(aButton):

The initial app screen, with a label and a blue button.

The initial state of the app

This is what we see when we debug the app and print the aLabel:

LLDB command po aLabel! prints the UILabel object and its properties.

Printing text property:

LLDB command po aLabel!.text returns the text Cursus Tortor Fusce Ornare Consectetur.

And changing it:

LLDB command po aLabel!.text = a quoted string changes the label text to a longer Lorem ipsum paragraph.

And boom! We have just changed the text here without re-build and re-run:

The app showing the updated label text without rebuilding.

After changing the text of the label

Let’s print the aButton:

LLDB command po aButton! prints the UIButton object and its properties.

Then print the backgroundColor property of aButton:

LLDB commands po aButton!.backgroundColor and po aButton!.backgroundColor! inspect the optional UIColor and its RGB components.

And changing it to redColor:

LLDB command po aButton!.backgroundColor = .red changes the button background to red.

Boom! We have changed the background color of the button from blue to red:

The app showing the red button after the debugger change.

After changing the background color of the button

Here as you see, we can easily debug and change a property of a UIView object in debugging. With this, we don’t have to re-build and re-run again and again for minimal changes.

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