I am aware there are more questions with the same title, but I couldn't find any other post with this specific case.
I have Xcode 7.0 and I want to update to the last version (7.3). But it doesn't appear in the updates page of the App Store. So, I searched for Xcode in the App Store and clicked the little update button. The button remains pressed and a loop icon appears on the top. But it stays like that for hours and there's no sign it's updating.
This doesn't seem to be working. I found in the internet that if I uninstall and reinstall it may work, but I don't want to lose all my projects.
Best Answer
Yes I always found updating Xcode from the App Store a painful experience.
Assuming you have an Apple ID*, you can bypass App Store and download it directly using this Apple Developer link and then find the version of Xcode you need.
As @Tetsujin says, also ensure you have an appropriate version of macOS to support the version of Xcode you are going to be running.
Note: * You no longer need a developer account, although you may want to consider this depending on the type of development you are going to be doing. See this Apple Developer page for details and links to create the appropriate account types. Note that you can start with a free Apple ID and upgrade later as necessary.