src/Observable.php
public function distinctKey(callable $keySelector, callable $comparer = null): Observable
    {
        return $this->lift(function () use ($keySelector, $comparer) {
            return new DistinctOperator($keySelector, $comparer);
        });
    }
public function distinctKey(callable $keySelector, callable $comparer = null): Observable
    {
        return $this->lift(function () use ($keySelector, $comparer) {
            return new DistinctOperator($keySelector, $comparer);
        });
    }
public function distinctKey ( callable $ keySelector , callable $ comparer = null ) : Observable { return $ this -> lift ( function ( ) use ( $ keySelector , $ comparer ) { return new DistinctOperator ( $ keySelector , $ comparer ) ; } ) ; }
Variant of distinct that takes a key selector

@param callable|null $keySelector
@param callable|null $comparer
@return Observable

@demo distinct/distinctKey.php
@operator
@reactivex distinct
Variant of distinct that takes a key selector