NSDateFormatter expense

Question

How expensive creation/modification of DateFormatters is? Is it cheaper to create 4 slightly different DateFormatters or modify a single DateFormatter?

I vaguely remember that modifying DateFormatters was as expensive as modifying GL Context (that is: very).

There is a dated discussion on the topic Why is allocating or initializing NSDateFormatter considered "expensive"?

Answer 1

func testPerformanceExampleUpdateFormat() {
    self.measure {
        (0...1_000).forEach { _ in
            let df = DateFormatter()
            df.dateFormat = "MMM yyyy"
            let formattedDate1 = df.string(from: Date())
            df.dateFormat = "MM/dd/yyyy"
            let formattedDate2 = df.string(from: Date())
        }
    }
}

func testPerformanceExampleNewInstance() {
    self.measure {
        (0...1_000).forEach { _ in
            let df1 = DateFormatter()
            df1.dateFormat = "MMM yyyy"
            let df2 = DateFormatter()
            df2.dateFormat = "MM/dd/yyyy"
            let formattedDate1 = df1.string(from: Date())
            let formattedDate2 = df2.string(from: Date())
        }
    }
}

• Result time when updating a format 1 000 times: 0.0896 s.

• Result time when creating a new instance 1 000 times: 0.138 s.

How expensive is a type?

func testPerformanceExample() {
    self.measure {
                    (0...1_000).forEach { _ in
            let int = DateFormatter()
        }
    }
}

The result time is 0.0017 s. for 1 000 instances of DateFormat

Let's compare it to other types:

0.000883 s. for 1 000 instances of Int; // let int = 2

0.000814 s. for 1 000 instances of String; // let str = String("Hello")

0.00118 s. for 1 000 instances of Date; // let date = Date()

0.0784 s. for 1 000 instances of UITableViewController; let vc = UITableViewController()

0.246 s. for 1 000 instances of UITableView; // let tv = UITableView()

Is it expensive?