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214baeae8b
the return type must be Observable<ValidationErrors | null> instead of Observable<ValidationErrors> | null PR Close #47465
30 lines
878 B
Markdown
30 lines
878 B
Markdown
@name Wrong Async Validator Return Type
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@category forms
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@shortDescription Async validator must return a Promise or Observable
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@description
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Async validators must return a promise or an observable, and emit/resolve them whether the validation fails or succeeds. In particular, they must implement the [AsyncValidatorFn API](api/forms/AsyncValidator)
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```typescript
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export function isTenAsync(control: AbstractControl):
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Observable<ValidationErrors | null> {
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const v: number = control.value;
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if (v !== 10) {
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// Emit an object with a validation error.
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return of({ 'notTen': true, 'requiredValue': 10 });
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}
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// Emit null, to indicate no error occurred.
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return of(null);
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}
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```
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@debugging
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Did you mistakenly use a synchronous validator instead of an async validator?
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<!-- links -->
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<!-- external links -->
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<!-- end links -->
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@reviewed 2022-06-28
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