Why does Xcode stop giving text prediction?

I am trying to learn how to create apps using Xcode. I usually follow tutorials on the web like Objective-C and Swift with built-in methods and functions that are usually hard to remember (at least for me at this stage). During the whole project, I no longer get the predictive text and have to type the whole method by word, which is not so bad but may take longer.

I wonder if anyone knows how to stop this behavior. I searched for some topics and found that I need to clean my project and restart Xcode. I tried this (which usually takes more time than typing at all) but it still doesn't work. In the same project, the predictive text seems to have stopped.

If I open another project, it works.

Just to clarify, by smart text I mean writing "UIView" and getting a dropdown menu with everything I would type as "UIViewController".

Thanks for all the help expected.