Federighi said: " the team that does the Dock and the window management on OS X, implemented all their new features for El Capitan in Swift and started mass-co

Federighi said: " the team that does the Dock and the window management on OS X, implemented all their new features for El Capitan in Swift and started mass-converting all of their code, and say that they couldn’t imagine going back and that they’re more productive with it." So the window management team is also using it.