Apple is beginning to bake Swift into some of its core software, instead of simply supporting it in third-party apps, senior VP of Software Engineering Craig Federighi said in a podcast interview.
The iCloud team has been "completely champing at the bit to be able to apply it in many, many of the things they do," the executive told Daring Fireball's John Gruber. More importantly Federighi noted that the team that does Dock and window management for OS X implemented of all of its El Capitan features in Swift, and has worked on mass-converting its code.
The group said "they couldn't imagine going back and that they're more productive with it [Swift]," according to Federighi.
He admitted that one problem Apple teams have is that they're often working with Swift in a prerelease state. With Swift 2.0 finished, however, current code development is said to be more stable.
On the subject of Swift going open-source earlier this month, Federighi suggested the move was because Apple wants Swift to be the main language programmers are taught. The company sees Swift potentially being "the major language for the next 20 years of programming in our industry," in Federighi's words.
The VP also commented that Swift is already the most active language on Github and that as a result, Apple's Swift group is more involved with developers than any other team in the company.