Call a async function when a variable is changed

Question

I have a @State variable and async function. I want to call the async function whenever that variable is changed.

Basically, what I am trying to do

VStack {
    Text("")
}
.onChange(of: var) { newValue in
    await asyncFunction()
}

But this gives me the following error

Cannot pass function of type '(Int) async -> ()' to parameter expecting synchronous function type

Nirav D · Accepted Answer · 2022-09-13 08:42:37Z

9

You cannot directly call an async function in the synchronous function. You need to wrap your call in Task or else you need to declare your function as async. Now in this case you cannot make your onChange action async so you need to wrap your call with Task.

Task { 
    await asyncFunction() 
}

answered Sep 13, 2022 at 8:42

Nirav D

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Comments

Joakim Danielson · Accepted Answer · 2025-04-21 14:11:27Z

2

If your var property conforms to Equatable you can use the task(id:) modifier

VStack {
    Text("")
}
.task(id: var) { 
    await asyncFunction()
}

answered Apr 21 at 14:11

Joakim Danielson

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1 Comment

Alexander Sandberg Apr 22 at 5:57

Keep in mind that this will call the function when the view initially appears as well, not only when the variable is changed.

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