swift2 - How do you enumerate OptionSetType in Swift? -

i have custom optionsettype struct in swift. how can enumerate values of instance?

this optionsettype:

struct weekdayset: optionsettype {     let rawvalue: uint8      init(rawvalue: uint8) {         self.rawvalue = rawvalue     }      static let sunday        = weekdayset(rawvalue: 1 << 0)     static let monday        = weekdayset(rawvalue: 1 << 1)     static let tuesday       = weekdayset(rawvalue: 1 << 2)     static let wednesday     = weekdayset(rawvalue: 1 << 3)     static let thursday      = weekdayset(rawvalue: 1 << 4)     static let friday        = weekdayset(rawvalue: 1 << 5)     static let saturday      = weekdayset(rawvalue: 1 << 6) } 

i this:

let weekdays: weekdayset = [.monday, .tuesday] weekday in weekdays {     // weekday } 

as of swift 4, there no methods in standard library enumerate elements of optionsettype (swift 2) resp. optionset (swift 3, 4).

here possible implementation checks each bit of underlying raw value, , each bit set, corresponding element returned. "overflow multiplication" &* 2 used left-shift because << defined concrete integer types, not integertype protocol.

swift 2.2:

public extension optionsettype rawvalue : integertype {      func elements() -> anysequence<self> {         var remainingbits = self.rawvalue         var bitmask: rawvalue = 1         return anysequence {             return anygenerator {                 while remainingbits != 0 {                     defer { bitmask = bitmask &* 2 }                     if remainingbits & bitmask != 0 {                         remainingbits = remainingbits & ~bitmask                         return self(rawvalue: bitmask)                     }                 }                 return nil             }         }     } } 

example usage:

let weekdays: weekdayset = [.monday, .tuesday] weekday in weekdays.elements() {     print(weekday) }  // output: // weekdayset(rawvalue: 2) // weekdayset(rawvalue: 4) 

swift 3:

public extension optionset rawvalue : integer {      func elements() -> anysequence<self> {         var remainingbits = rawvalue         var bitmask: rawvalue = 1         return anysequence {             return anyiterator {                 while remainingbits != 0 {                     defer { bitmask = bitmask &* 2 }                     if remainingbits & bitmask != 0 {                         remainingbits = remainingbits & ~bitmask                         return self(rawvalue: bitmask)                     }                 }                 return nil             }         }     } } 

swift 4:

public extension optionset rawvalue: fixedwidthinteger {      func elements() -> anysequence<self> {         var remainingbits = rawvalue         var bitmask: rawvalue = 1         return anysequence {             return anyiterator {                 while remainingbits != 0 {                     defer { bitmask = bitmask &* 2 }                     if remainingbits & bitmask != 0 {                         remainingbits = remainingbits & ~bitmask                         return self(rawvalue: bitmask)                     }                 }                 return nil             }         }     } }