how to set cookies in inner function

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how to fix this code.

add_action( 'wp_head', array( $this, 'update_view' ));
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public function update_view() {
                global $post;
		if ( is_singular( 'dwqa-question' ) ) {
                        $cookie_name = $post->ID.'_dwqa_who_viewed';
                        $cookie_value = 1 ;

                            if(isset($_COOKIE[$cookie_name]) && $_COOKIE[$cookie_name] == 'true' ) {
                                echo "Cookie '" . $cookie_name . "' is set!<br>";
                                echo "Value is: " . $_COOKIE[$cookie_name];

                                $refer = wp_get_referer();
                                if ( is_user_logged_in() ) {
                                        global $current_user;
                                        //save who see this post
                                        $viewed = get_post_meta( $post->ID, '_dwqa_who_viewed', true );
                                        $viewed = ! is_array( $viewed ) ? array() : $viewed;
                                        $viewed[$current_user->ID] = current_time( 'timestamp' );
                                }

                                if ( ( $refer && $refer != get_permalink( $post->ID ) ) || ! $refer ) {
                                        if ( is_single() && 'dwqa-question' == get_post_type() ) {
                                                $views = get_post_meta( $post->ID, '_dwqa_views', true );

                                                if ( ! $views ) {
                                                        $views = 1;
                                                } else {
                                                        $views = ( ( int ) $views ) + 1;
                                                }
                                                update_post_meta( $post->ID, '_dwqa_views', $views );
                                        }
                                }
                        }else{
                            setcookie( $cookie_name, $cookie_value, time() + DAY_IN_SECONDS,COOKIEPATH, COOKIE_DOMAIN, false, false );
                            echo "Cookie named '" . $cookie_name . "' is not set!";
                        }
                }
	}