I'm pretty sure that you all have a macintosh computer with Xcode tools installed on it, make sure it is a version that works on your pesonal system. If not please get it or leave this topic.
If you are here, you should be able to do this.
Directions:To start, open Finder.Then, open the developer folder.Open Examples from that folder.Then, open the TextEdit FolderOpen textedit.xcodeprojNow Xcode should open.
Once Xcode is open you'll be able to browse that source code of TextEdit.
If you click Build and Go, TextEdit will open.