I have a Button which is disabled depending on an isSubmitDisabled
function which is defined as async
because it has an async
part.
<Button type="button" disabled={isSubmitDisabled()}>Submit</Button>
const isSubmitDisabled = async () => {
let result1 = await validatePart1(..);
//...
return finalResult ? true : false;
}
The validation works, but I can’t use the prop expression syntax above for disabled=
.
If I do disabled={isSubmitDisabled()}>
error: Type ‘true | Promise’ is not assignable to type ‘boolean | undefined’.
Type ‘Promise’ is not assignable to type ‘boolean | undefined’.ts(2322)
If I do disabled={await isSubmitDisabled()}>
error: ‘await’ expressions are only allowed within async functions and at the top levels of modules
If I do a wrapper function per this example:
disabled = {
(async () => {
await isSubmitDisabled()
})()
}
error: Type ‘Promise’ is not assignable to type ‘boolean | undefined’.
2
Answers
You can’t synchronously get a value from an asynchronous operation.
Use a state value to drive the UI, and update that state value from the asynchronous operation. For example, consider a simple boolean state:
Use that value to drive the button:
Then you can update that state value from the asynchronous operation. When/where that operation is invoked is up to you, in this case I’m just adding it to a
useEffect
which is executed once when the component first loads:Depending on the structure of what you’re building, you may invoke this operation at a different time or even at multiple times. But however you structure it, the point is to use state as an intermediary for asynchronous values.
Create state to hold the disabled status.
Use useEffect to call the async function and update the state accordingly.