Unfortunately, the server response is not ideal. Here are two possible solutions:
- An approach assuming you cannot modify the response.
- An alternative suggesting a modification to the response. :-)
If Modifying the Response is Not Possible
If you are unable to change the response, you will have to use type assertions when extracting information from it (more details in the PR introducing TypeScript's handling of rest elements within a tuple — special thanks to jcalz for pointing that out).
The correct type for the response is:
type ResponseTuple = [...IFoo[], IBar];
To make things easier to manage, let's wrap the type assertions in a function that is reusable and testable:
// A utility function to split the response into a more manageable structure
function splitResponse(response: ResponseTuple): {bar: IBar, foos: IFoo[]} {
if (response.length < 1) {
// In case there is no bar in the response, throw an error (you can handle this differently based on your requirements)
throw new Error(`Cannot split an empty response`);
}
const bar = response[response.length - 1] as IBar;
const foos = response.slice(0, -1) as IFoo[];
return {bar, foos};
}
How to use the function:
const { bar, foos } = splitResponse(someResponse);
Playground example
If Modifying the Response is Possible
If you have the ability to modify the server response so that `IBar` comes first, the solution becomes significantly simpler:
// The updated type definition for the response
type ResponseTuple = [IBar, ...IFoo[]];
// Splitting the response
const [ bar, ...foos] = someResponse;
console.log(bar);
// ^? const bar: IBar
console.log(foos);
// ^? const foos: IFoo[]
Playground link