Xcode - search text in all files

Use cmd + shift + f for complete Xcode search.

On the left hand side of the editor you have a magnifying glass. There's a search box there. That should do the trick. (it's called the search navigator)

cmd + shift + f opens it too.

To do it simply from the UI, with a click

By default, this will be searching through the entire project searching for any files containing the specific string you entered.

From this point, you can start doing more stuffs like replace all, etc, like this

Use Command + 3 a minimum keyboard shortcut or Command + Shift + f

cmd + shift + f

then press return key of you keyboard.