My issue involves managing a list
export const list = [
{
name: 'parentTitle',
},
{
name: 'anotherTitle',
},
{
name: 'whatever',
},
];
My goal is to dynamically create a union type that reflects the titles in the list:
type Title = 'parentTitle' | 'anotherTitle' | 'whatever';
Is there a solution for accomplishing this?
I attempted to modify an approach found here: Keyof nested child objects However, I am struggling to figure it out
The compiler infers the type of the list in your example to be Array<{name: string}>. This means that the particular string literal types of the name properties are forgotten by the time you define Title.
To address this, you need to adjust how you assign values to list. One way to do this is to use a const assertion, which instructs the compiler to infer the narrowest possible type:
export const list = [
{ name: 'parentTitle', },
{ name: 'anotherTitle', },
{ name: 'whatever', },
] as const;
Now, list is inferred to have the following type:
/*
const list: readonly [
{ readonly name: "parentTitle";},
{ readonly name: "anotherTitle";},
{ readonly name: "whatever";}
]
*/
This represents a readonly tuple of readonly objects with specific name properties in a specified order. With this information, we can utilize lookup types to define Title:
type Title = typeof list[number]["name"];
// type Title = "parentTitle" | "anotherTitle" | "whatever"
That should provide some clarity on resolving the issue. Good luck!
To achieve this, follow these steps:
type GetTitles<T extends readonly {title: string}[]> = T[number]['title'];
const titleList = [
{
title: 'mainTitle',
},
{
title: 'secondaryTitle',
},
{
title: 'additionalTitle',
},
] as const;
//desired output
type titles = GetTitles<typeof titleList>; // 'mainTitle' | 'secondaryTitle' | 'additionalTitle'
Create an interface to define different titles and convert it into an array type.
interface TitleOptions {
title: 'main' | 'secondary' | 'other';
}
let titleList: TitleOptions[] = [
{
title: 'main',
},
{
title: 'secondary',
},
{
title: 'other',
},
];
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