52 lines
1.3 KiB
Plaintext
52 lines
1.3 KiB
Plaintext
/**
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Create a union of types that share a common discriminant property.
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Use-case: A shorter way to declare tagged unions with multiple members.
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@example
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```
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import type {TaggedUnion} from 'type-fest';
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type Tagged<Fields extends Record<string, unknown> = TaggedUnion<'type', Fields>
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// The TaggedUnion utility reduces the amount of boilerplate needed to create a tagged union with multiple members, making the code more concise.
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type EventMessage = Tagged<{
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OpenExternalUrl: {
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url: string;
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id: number;
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language: string;
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};
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ToggleBackButtonVisibility: {
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visible: boolean;
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};
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PurchaseButtonPressed: {
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price: number;
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time: Date;
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};
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NavigationStateChanged: {
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navigation?: string;
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};
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}>;
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// Here is the same type created without this utility.
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type EventMessage =
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| {
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type: 'OpenExternalUrl';
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url: string;
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id: number;
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language: string;
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}
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| {type: 'ToggleBackButtonVisibility'; visible: boolean}
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| {type: 'PurchaseButtonPressed'; price: number; time: Date}
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| {type: 'NavigationStateChanged'; navigation?: string};
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```
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@category Utilities
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*/
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export type TaggedUnion<
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TagKey extends string,
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UnionMembers extends Record<string, Record<string, unknown>>,
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> = {
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[Name in keyof UnionMembers]: {[Key in TagKey]: Name} & UnionMembers[Name];
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}[keyof UnionMembers];
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