How to change the style of the datePicker component ?

You have several existing styles:

• CompactDatePickerStyle

• DefaultDatePickerStyle

• FieldDatePickerStyle

• GraphicalDatePickerStyle

• StepperFieldDatePickerStyle

• WheelDatePickerStyle

you apply the modifier to the datePicker
.datePickerStyle(WheelDatePickerStyle())

How do you need to customise ? If none of those above styles, you have to create your own picker.

Yes I have already seen .datePickerStyle () and all these styles.
I would like to customize to display the dates on a single line in a horizontal scrollView.

example a bit like that

Code Block 
sun mon tue wen thu fri sat sun mon tue wen thu fri sat
 1   2   3   4   5   6   7   8   9   10  11  12   ..... 

Precisely it's for that I would like to create my own picker but I don't know how to do it, where to start.

You need to precise your spec a little.

How many days do you want to present ? Only the selected month ?

One way to do :

• create a scrollView

• each day is a 2 lines label that you set with the correct day name and number

• enable user interaction for each label, so that user can tap it

Or you can subclass UISegmentedControl.
Creating images as
  lun
    1

Code Block 
class PickerSegmentedControl: UISegmentedControl {
     
    var allImages : [UIImage] = []  // To be set before calling. Must be the right size
    func commonInit() {
         let numberOfDays = self.numberOfSegments
         for i in 0..<numberOfDays where i < allImages.count {
           self.setImage(allImages[i], forSegmentAt: i)
        }
     }
     override init(frame: CGRect) {
         super.init(frame: frame)
         commonInit()
     }
     required init?(coder aDecoder: NSCoder) {
          super.init(coder: aDecoder)
          commonInit()
     }
     
}

Thank you for your help