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How to call a function when a slider changes in SwiftUI

maeganwilson_ profile image Maegan Wilson Updated on ・2 min read

There are times you might want to call a function when a slider changes in SwiftUI. I did this recently to send out the slider's value to another device when the slider is moving. I couldn't wait to send out the final value since that would be a delayed response for the user.

After the code example, I'll explain the three steps.

import SwiftUI

struct SliderExample: View {
// 1. declare a state for the value of the slider
    @State private var value: Float = 0.0

// 2. create a slider with a new Binding variable
    var body: some View {
        Slider(value: Binding(
            get: {
                self.value
            },
            set: {(newValue) in
                  self.value = newValue
                  self.doSomething()
            }
        ))
    }

// 3. create the function to call when the slider changes value    
    func doSomething(){
        print("\(value)")
    }
}

1. Declare a state variable for the value of the slider

This is the variable that the slider is currently. It needs to be declared with a State property wrapper since the value is going to change. It also needs to have a Float type since a Slider needs a Binding<Float>.

2. Create a slider with a new binding variable

In this step, we are creating a Binding variable. A Binding variable is a computed property. By creating it as the value that the slider is using, we can utilize the setter to call the function every time the value is changing.

3. Create the function to call when the slider changes value

Make sure to make the function that you need to call when the slider changes values.


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Posted on by:

maeganwilson_ profile

Maegan Wilson

@maeganwilson_

I am an independent iOS developer and Apple product enthusiast.

Discussion

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Helped me a lot, but in "set:" it should be called either newVal or newValue.

 

Thanks for catching that! I'll update the post :)