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distinctUntilSomeChanged

distinctUntilSomeChanged

Returns an Observable that emits all items emitted by the source Observable that are distinct by comparison from the previous item. Comparison will be done for each set key in the keys array.

You can fine grain your distinct checks by providing a KeyCompareMap with those keys you want to compute explicitly different

The name distinctUntilSomeChanged was picked since it internally iterates over the keys and utilizes the some method in order to compute if values are distinct or not.

Example

import { of } from 'rxjs';
import { distinctUntilSomeChanged } from 'rx-angular/state';

interface Person {
age: number;
name: string;
}

of(
{ age: 4, name: 'Hans' },
{ age: 7, name: 'Sophie' },
{ age: 5, name: 'Han Solo' },
{ age: 5, name: 'HanSophie' }
)
.pipe(distinctUntilSomeChanged(['age', 'name']))
.subscribe((x) => console.log(x));

// displays:
// { age: 4, name: 'Hans'}
// { age: 7, name: 'Sophie'}
// { age: 5, name: 'Han Solo'}
// { age: 5, name: 'HanSophie'}

Example

// An example with `KeyCompareMap`
import { of } from 'rxjs';
import { distinctUntilSomeChanged } from 'rxjs/operators';

interface Person {
age: number;
name: string;
}
const customComparison: KeyCompareMap<Person> = {
name: (oldName, newName) =>
oldName.substring(0, 2) === newName.substring(0, 2),
};

of(
{ age: 4, name: 'Hans' },
{ age: 7, name: 'Sophie' },
{ age: 5, name: 'Han Solo' },
{ age: 5, name: 'HanSophie' }
)
.pipe(distinctUntilSomeChanged(['age', 'name'], customComparison))
.subscribe((x) => console.log(x));

// displays:
// { age: 4, name: 'Hans' }
// { age: 7, name: 'Sophie' }
// { age: 5, name: 'Han Solo' }

Signature

function distinctUntilSomeChanged<T extends object, K extends keyof T>(
keys: K[],
keyCompareMap?: KeyCompareMap<T>
): MonoTypeOperatorFunction<T>;

Parameters

keys

typeof: K[]

keyCompareMap

typeof: KeyCompareMap<T>