Plugin that would allow WordPress Authors to "follow" other Authors and query "Activity Info" from that

Question

I have a WordPress blog that is all user based Authors that submit content and such. Currently in the site, you can view other authors profiles but basically just view their content from the author.php template.

Where would I even begin to build a plugin (or find a plugin) that allows authors to "follow" other authors and then on another page query the authors they follow to show certain content from their followed authors like comments they made, posts they made, etc.

I don't want to add BuddyPress or go that route but I have seen similar plugins for BuddyPress but not for just WordPress.

I imagine I need to do something like create an array of users they follow in their user meta then query those users to display the "activity". Is that sound right?. Any insights, tutorials, plugins etc that may help get my foot in the door for this?

Thanks!

Answer 1

Just a plugin concept …

1. Add a form with a button to each user profile, post or wherever you want it named Follow or Unfollow. Show the button only if is_user_logged_in(). You may use a widget for the form.

2. On form submit update a user meta named follows for the user who clicked the button and another one named followers for … well … the user who just got a new follower. Use the user IDs as a serialized array (yes, ugly, I know). Or use a custom table, that might work better and faster.

3. Create a dashboard widget or a whole page where the access is restricted to users who can follow or be followed. Query for the user meta follows to get a list of all authors the current user has subscribed to and then query for the posts from these users.

4. Get the user meta followers and print a nice list of her followers.

Answer 2

mbtNewsFeed Plugin

Any feedback is welcome!

Edit

We discussed about OOP and code design, so there is now a version matching the community requirements. Same principle, same result, but a function based design. – Thanks go to Pieter Goosen and Mark Kaplun for the feedback

Step-by-step:

Thanks to @toscho for the conceptual design

Let's try to wrap it up. We need a button to un/follow a user

function mbt_news_feed_button($user_id, $follow=true) {
    $class = 'unfollow';
    $label = __('Unfollow','newsfeed');
    if (true === $follow) {
        $class = 'follow';
        $label = __('Follow','newsfeed');
    }
    return "<a href='#mbt-news-feed' class='button {$class}' data-user_id='{$user_id}'>{$label}</a>";
}

We want to manipulate the follow status of a user. We create two functions: One to follow and one to unfollow.

function mbt_follow() {
    $user_id = self::helper_check_data();
    $current_user = wp_get_current_user();
    $followers = get_user_meta( $current_user->ID, 'following', true);
    if (!is_array($followers)){
        $followers = array();
    }
    $followers[$user_id] = 1;
    update_user_meta( $current_user->ID, 'following', $followers );
    echo self::button($user_id, true);
    exit;
}

function mbt_unfollow() {
    $user_id = self::helper_check_data();
    $current_user = wp_get_current_user();
    $followers = get_user_meta( $current_user->ID, 'following', true);
    if (is_array($followers) && !empty($followers)){
        unset($followers[$user_id]);
    } else {
        $followers = array();
    }
    update_user_meta( $current_user->ID, 'following', $followers );
    echo self::button($user_id, false);
    exit;
}

To help us validating the ajax nonce and filtering the input a helper function is needed.

function mbt_news_feed_helper_check_data() {
    if(!wp_verify_nonce( $_POST['_ajax_nonce'], 'mbtNewsFeed' )) {
        die(-1);
    }
    if (!array_key_exists('user_id', $_POST)) {
        die(-1);
    }
    $user_id = absint($_POST['user_id']);
    if ($user_id < 1) {
        die(-1);
    }
    return $user_id;
}

To check if the logged in user is currently following the user in question we need another function

function mbt_news_feed_is_following($user_id) {
    $followers = get_user_meta( $user_id, 'following', true);
    if (empty($followers)) {
        return false;
    }
    if (array_key_exists($user_id, $followers) && $followers[$user_id]) {
        return true;
    }
    return false;
}

We like to keep things clean and tidy, so we create a function that returns an array of all valid AJAX calls for this class

mbt_news_feed_function valid_actions() {
    return array(
        'mbt_follow',
        'mbt_unfollow',
    );
}

We want to make our AJAX calls work, so we register our actions outside the class

if (is_admin()){
    foreach (mbt_news_feed_valid_actions() as $action) {
        add_action('wp_ajax_'.$action, $action);
    }
}

Then we want to call the actions too if requested via AJAX

function mbt_news_feed_init() {
    if(in_array($_REQUEST['action'], mbt_news_feed_valid_actions())) {
        do_action( 'wp_ajax_' . $_REQUEST['action'] );
    }
}

To make the button we created work we need some JS.

jQuery(document).ready(function($) {
    $('body').on('click', '#mbt-news-feed .follow, #mbt-news-feed .unfollow', function(e) {
        e.preventDefault();
        var $me = $(this),
            action = 'mbt_follow';
        if ($me.hasClass('unfollow')) action = 'mbt_unfollow';
        var data = $.extend(true, $me.data(), {
            action: action,
            _ajax_nonce: admin_ajax.nonce
        });
        $.post(admin_ajax.url, data, function(response) {
            if(response == '0' || response == '-1'){
            } else {
                $($me).parent().empty().html(response);
            }
        });
    });
});

To get the admin AJAX URL and our nonce in the frontend, we need to enqueue and localize the script and enqueue jQuery too, if not already loaded. To save on loading time, we put the script in the footer.

function mbt_news_feed_enqueue_scripts() {
    if (is_user_logged_in()) {
        wp_enqueue_script('jquery');
        wp_enqueue_script( 'mbt-news-feed', plugins_url('newsfeed.js', __FILE__), array('jquery'), NULL, true);
        wp_localize_script('mbt-news-feed', 'admin_ajax', array(
            'url' => admin_url('admin-ajax.php'),
            'nonce' => wp_create_nonce('mbtNewsFeed'),
        ));
        wp_enqueue_style( 'mbt-news-feed-css', plugins_url('newsfeed.css', __FILE__) );
    }
}

Now we need to display our button on certain pages, (single post/page templates and author archive templates)

function mbt_news_feed_wp_footer() {
    if (is_user_logged_in()) {
        $render_button = false;
        $user_id = 0;
        if (is_singular()) {
            $render_button = true;
            $post_id = get_queried_object_id();
            $user_id = get_post_field( 'post_author', $post_id );
        }
        if (is_author()) {
            $render_button = true;
            $user_id = get_queried_object_id();
        }
        if (true === $render_button && $user_id > 0) {
            $follow = self::is_following($user_id);
            echo "<div id='mbt-news-feed'>";
            echo self::button($user_id, !$follow);
            echo "</div>";
        }
    }
}

Before we add all the action we need to filter the posts on the home page. If the user is logged in and follows at least one other author, we will show his individual feed.

static function pre_get_posts($query) {
    if (is_user_logged_in()) {
        if ( $query->is_main_query() && $query->is_home() && !is_admin()) {
            $current_user = wp_get_current_user();
            $followers = get_user_meta( $current_user->ID, 'following', true);
            if (is_array($followers) && !empty($followers)) {
                $followers = array_keys($followers);
                $followers[] = $current_user->ID;
                $query->set('author__in', $followers);
            }
        }
    }
    return $query;
}

Now adding some actions to make the plugin finally work

add_action( 'init', 'mbt_news_feed_init');
add_action( 'wp_enqueue_scripts', 'mbt_news_feed_enqueue_scripts');
add_action( 'pre_get_posts', 'mbt_news_feed_pre_get_posts');
add_action( 'wp_footer', 'mbt_news_feed_wp_footer');

And don't forget the CSS to display your button properly.

Files

newsfeed.php

/**
 * mbtNewsFeed for purists
 *
 * @package     mbtNewsFeed
 * @author      iantsch
 * @copyright   2016 mbt.wien
 * @license     GPL-2.0+
 *
 * @wordpress-plugin
 * Plugin Name: mbtNewsFeed
 * Plugin URI:  http://wordpress.stackexchange.com/questions/41934/
 * Description: If you are logged in and follow some authors, the home feed will only show their posts.
 * Version:     1.0.0
 * Author:      iantsch
 * Author URI:  http://mbt.wien
 * Text Domain: newsfeed
 * License:     GPL-2.0+
 * License URI: http://www.gnu.org/licenses/gpl-2.0.txt
 */


function mbt_news_feed_init() {
    if(in_array($_REQUEST['action'], mbt_news_feed_valid_actions())) {
        do_action( 'wp_ajax_' . $_REQUEST['action'] );
    }
}

function mbt_news_feed_pre_get_posts($query) {
    if (is_user_logged_in()) {
        if ( $query->is_main_query() && $query->is_home() && !is_admin()) {
            $current_user = wp_get_current_user();
            $followers = get_user_meta( $current_user->ID, 'following', true);
            if (is_array($followers) && !empty($followers)) {
                $followers = array_keys($followers);
                $followers[] = $current_user->ID;
                $query->set('author__in', $followers);
            }
        }
    }
    return $query;
}

function mbt_news_feed_is_following($user_id) {
    $followers = get_user_meta( $user_id, 'following', true);
    if (empty($followers)) {
        return false;
    }
    if (array_key_exists($user_id, $followers) && $followers[$user_id]) {
        return true;
    }
    return false;
}

function mbt_news_feed_helper_check_data() {
    if(!wp_verify_nonce( $_POST['_ajax_nonce'], 'mbtNewsFeed' )) {
        die(-1);
    }
    if (!array_key_exists('user_id', $_POST)) {
        die(-1);
    }
    $user_id = absint($_POST['user_id']);
    if ($user_id < 1) {
        die(-1);
    }
    return $user_id;
}

function mbt_follow() {
    $user_id = mbt_news_feed_helper_check_data();
    $current_user = wp_get_current_user();
    $followers = get_user_meta( $current_user->ID, 'following', true);
    if (!is_array($followers)){
        $followers = array();
    }
    $followers[$user_id] = 1;
    update_user_meta( $current_user->ID, 'following', $followers );
    echo mbt_news_feed_button($user_id, false);
    exit;
}

function mbt_unfollow() {
    $user_id = mbt_news_feed_helper_check_data();
    $current_user = wp_get_current_user();
    $followers = get_user_meta( $current_user->ID, 'following', true);
    if (is_array($followers) && !empty($followers)){
        unset($followers[$user_id]);
    } else {
        $followers = array();
    }
    update_user_meta( $current_user->ID, 'following', $followers );
    echo mbt_news_feed_button($user_id, true);
    exit;
}

function mbt_news_feed_button($user_id, $follow=true) {
    $class = 'unfollow';
    $label = __('Unfollow','newsfeed');
    if (true === $follow) {
        $class = 'follow';
        $label = __('Follow','newsfeed');
    }
    return "<a href='#mbt-news-feed' class='button {$class}' data-user_id='{$user_id}'>{$label}</a>";
}

function mbt_news_feed_valid_actions() {
    return array(
        'mbt_follow',
        'mbt_unfollow',
    );
}

function mbt_news_feed_enqueue_scripts() {
    if (is_user_logged_in()) {
        wp_enqueue_script('jquery');
        wp_localize_script('jquery', 'admin_ajax', array(
            'url' => admin_url('admin-ajax.php'),
            'nonce' => wp_create_nonce('mbtNewsFeed'),
        ));
        wp_enqueue_script( 'mbt-news-feed', plugins_url('newsfeed.js', __FILE__), array('jquery'), NULL, true);
        wp_enqueue_style( 'mbt-news-feed-css', plugins_url('newsfeed.css', __FILE__) );
    }
}

function mbt_news_feed_wp_footer() {
    if (is_user_logged_in()) {
        $render_button = false;
        $user_id = 0;
        if (is_singular()) {
            $render_button = true;
            $post_id = get_queried_object_id();
            $user_id = get_post_field( 'post_author', $post_id );
        }
        if (is_author()) {
            $render_button = true;
            $user_id = get_queried_object_id();
        }
        if (true === $render_button && $user_id > 0) {
            $follow = mbt_news_feed_is_following($user_id);
            echo "<div id='mbt-news-feed'>";
            echo mbt_news_feed_button($user_id, !$follow);
            echo "</div>";
        }
    }
}

if (is_admin()){
    foreach (mbt_news_feed_valid_actions() as $action) {
        add_action('wp_ajax_'.$action, $action);
    }
}

add_action( 'init', 'mbt_news_feed_init');
add_action( 'wp_enqueue_scripts', 'mbt_news_feed_enqueue_scripts');
add_action( 'pre_get_posts', 'mbt_news_feed_pre_get_posts');
add_action( 'wp_footer', 'mbt_news_feed_wp_footer');

newsfeed.js

jQuery(document).ready(function($) {
    $('body').on('click', '#mbt-news-feed .follow, #mbt-news-feed .unfollow', function(e) {
        e.preventDefault();
        var $me = $(this),
            action = 'mbt_follow';
        if ($me.hasClass('unfollow')) action = 'mbt_unfollow';
        var data = $.extend(true, $me.data(), {
            action: action,
            _ajax_nonce: admin_ajax.nonce
        });
        $.post(admin_ajax.url, data, function(response) {
            if(response == '0' || response == '-1'){
            } else {
                $($me).parent().empty().html(response);
            }
        });
    });
});

newsfeed.css

#mbt-news-feed {
    display: block;
    position: fixed;
    bottom: 20px;
    bottom: 3.125vw;
    right: 20px;
    right: 3.125vw;
}

#mbt-news-feed a.button{
    display: block;
    border-radius: 2px;
    border-radius: 0.625vw;
    padding: 5px 10px;
    padding: 1.5625vw 3.125vw;
    color: #fff;
    background-color: #333;
    background-color: rgba(51,51,51,.8);
    opacity: .5;
}

#mbt-news-feed a.button:hover{
    opacity: 1;
}