UIDatePicker Date Change Listener : Swift
Adding an editing event to a UIDatePicker is something that is required most of the time. For views like UIDatePicker, we can connect an IBAction with the event type as value changed and get a callback for the value changed.
This post was originally posted at https://agrawalsuneet.github.io/blogs/uidatepicker-date-change-listener-swift/ and reposted on Medium on 12th April 2022.If you are not using xib or storyboard but creating the layout programmatically or by using swiftUI, you can the editing event using a target action that takes three parameters,
- target of Any type which is nullable
- action of Selector type
- controlEvents of UIControl.Event
The code for the same will look like below.
//swift code in viewcontrollerself.datePicker.addTarget(self, action: #selector(onDateValueChanged(_:)), for: .valueChanged) @objc private func onDateValueChanged(_ datePicker: UIDatePicker) {
//do something here
}
Since the Selector takes only @objc functions which can only be defined as a member of the class or an extension of the class, we need to define it at a class level only.
@objc can only be used with members of classes, @objc protocols, and concrete extensions of classesThis way is a bit inefficient as we need to add one function for each UIDatePicker where we need editing event.
There is a better way where we can add this functionality to each UIDatePicker without making our class messy.
We can add this to the UIDatePicker extension itself which will be a very clean approach and will make our life super easy.
First, add a function as an extension to UIDatePicker class which takes a function as a parameter with 0 params and Void return type.
Since this function will be our callback function, add @escaping to the function passed as the parameter.
//MARK: - UIDatePicker Extension
extension UIDatePicker {
func setOnDateChangeListener(onDateChanged :@escaping () -> Void){
}
}