Something to keep in mind when creating formatters is to try to reuse the same instance if you can, as formatters are fairly computationally expensive to create. The following is a pattern I frequently use for apps where I can share the same formatter app-wide, adapted from NSHipster.
extension DateFormatter {
static var sharedDateFormatter: DateFormatter = {
let dateFormatter = DateFormatter()
// Add your formatter configuration here
dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
return dateFormatter
}()
}
Usage:
let dateString = DateFormatter.sharedDateFormatter.string(from: Date())