In your example, it's important to remember that while there are seemingly endless amounts of tutorials, etc. on the 'net etc. the tools advance at a rate that tends to obsolete them very quickly.
For newbies, this presents a mine field of liability where the skill to know how to tread is typically missing.
In your case, you may want to start by stating which version Xcode you're using, and by quoting any errors, specifically, rather than paraphrasing. Feel free to add a bit of the related code to your question. See: For Best Results - Read the Label
As well, until you get your feet underneath you, it might be better to stick with Apple's tutorials, direct from the mothership.
About use of undeclared type, there can be a raft of issues - see this SO thread for examples:https://stackoverflow.com/questions/38515522/swift-use-of-undeclared-type?rq=1
...but again, without seeing your code, it's hard to even guess.
where im stuggling is that im following the exact walk thought and not getting the same, im using Xcode 10.1, it almost that the same code isnt avalible within this version.
I got that, thanks, no need to repeat.
Did you understand my point about how many tutorials lag behind the tools? And the need to share some code if you want specific help?
Might be best if you put that tutorial aside and, again, looked for something from Apple, instead. No point in learning how to wedge outdated code into current tools when all you want to do is start learning the tools themselves.
If you're stuck on cold-casing that tutorial, you may want to spend time finding the author and asking them for help with their content. Not sure I'd bother in your example, tho.
Why be so secretive, if you want help.
USE OF UNDECLARED TYPE.....
Instead of suspension points, give the type !
And post the code where you get the error, with the complete class definition if possible.