Where do I find the line number in the Xcode editor?
Solution 1:
For Xcode 4 and higher, open the preferences (command+,) and check "Show: Line numbers" in the "Text Editing" section.
Xcode 9
Xcode 8 and below
Solution 2:
In Preferences->Text Editing-> Show: Line numbers you can enable the line numbers on the left hand side of the file.