SwiftUI has a Picker view available with multiple different styles. One example of when it falls short is when we want to use a multi component picker with wheel style. One way how to try to achieve this is using a HStack with two Picker views, but it does not work very well, especially when trying to show it inside a Form view. So what else we can do? If something can’t be done in SwiftUI then we can use UIKit instead.
In my case, I wanted to create a picker which allows picking a date duration. It would have one wheel for selecting a number and the other wheel for selecting either days, weeks or months.
Firstly, let’s create a tiny struct which is going to hold the state of this picker. It needs to store a numeric value and the unit: days, weeks, months. Let’s name it as DateDuration. Since we want to iterate over the DateDuration.Unit, we’ll conform it to CaseIterable protocol.
UIPickerView in UIKit can do everything we want, therefore we’ll need to wrap it into a SwiftUI view. This can be done by creating a new type which conforms to UIViewRepresentable protocol. Also, we need a binding which holds the value of the current selection: when the user changes it, the binding communicates the changes back and vice-versa. Additionally, we’ll add properties for configuring values and units. UIPickerView us created and configured in the makeUIView(context:) function. UIPickerView is driven by a data source and a delegate, which means we require a coordinator object as well. Coordinator is part of the UIViewRepresentable protocol.
Coordinator is created in the makeCoordinator() function. It is going to do most of the work by providing data to the UIPickerView and handling the current selection. Therefore, we’ll store the selection binding, values, and units in the Coordinator class as well.
The last missing piece is implementing UIPickerViewDataSource and UIPickerViewDelegate methods in the Coordinator class. This is pretty straight-forward to do. We’ll need to display two components where the first component is the list of values and the second component is the unit: days, weeks, months. When the user selects a new value, we’ll change the DateDuration value of the binding.
Finally, let’s hook it up in an example view.
SwiftUIDateDurationPicker (GitHub, Xcode 13.2.1)