86 lines
2.4 KiB
Markdown
86 lines
2.4 KiB
Markdown
---
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id: BaseQueryNarrowing
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title: BaseQueryNarrowing
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---
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Defined in: [packages/angular-query-experimental/src/types.ts:83](https://github.com/TanStack/query/blob/main/packages/angular-query-experimental/src/types.ts#L83)
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The `isSuccess`/`isError`/`isPending` methods on a query result. Unlike `react-query`'s derived booleans,
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these are type-guard methods you call — `if (query.isSuccess())` — so that `query.data` narrows away
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`undefined` inside the branch, the same way `status` narrowing works on the plain object `react-query`
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returns.
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## Type Parameters
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### TData
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`TData` = `unknown`
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The type `data` ends up as after `select` runs.
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### TError
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`TError` = [`DefaultError`](../type-aliases/DefaultError.md)
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The type of errors your `queryFn` may throw.
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## Properties
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### isError()
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```ts
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isError: (this) => this is CreateBaseQueryResult<TData, TError, CreateStatusBasedQueryResult<"error", TData, TError>>;
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```
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Defined in: [packages/angular-query-experimental/src/types.ts:91](https://github.com/TanStack/query/blob/main/packages/angular-query-experimental/src/types.ts#L91)
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#### Parameters
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##### this
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[`CreateBaseQueryResult`](../type-aliases/CreateBaseQueryResult.md)\<`TData`, `TError`\>
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#### Returns
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`this is CreateBaseQueryResult<TData, TError, CreateStatusBasedQueryResult<"error", TData, TError>>`
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***
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### isPending()
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```ts
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isPending: (this) => this is CreateBaseQueryResult<TData, TError, CreateStatusBasedQueryResult<"pending", TData, TError>>;
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```
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Defined in: [packages/angular-query-experimental/src/types.ts:98](https://github.com/TanStack/query/blob/main/packages/angular-query-experimental/src/types.ts#L98)
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#### Parameters
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##### this
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[`CreateBaseQueryResult`](../type-aliases/CreateBaseQueryResult.md)\<`TData`, `TError`\>
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#### Returns
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`this is CreateBaseQueryResult<TData, TError, CreateStatusBasedQueryResult<"pending", TData, TError>>`
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***
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### isSuccess()
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```ts
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isSuccess: (this) => this is CreateBaseQueryResult<TData, TError, CreateStatusBasedQueryResult<"success", TData, TError>>;
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```
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Defined in: [packages/angular-query-experimental/src/types.ts:84](https://github.com/TanStack/query/blob/main/packages/angular-query-experimental/src/types.ts#L84)
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#### Parameters
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##### this
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[`CreateBaseQueryResult`](../type-aliases/CreateBaseQueryResult.md)\<`TData`, `TError`\>
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#### Returns
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`this is CreateBaseQueryResult<TData, TError, CreateStatusBasedQueryResult<"success", TData, TError>>`
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