Cacher is the code snippet organizer for pro developers

<?php
// Where you are assigning *_books capabilities to users:

register_post_type( 'book', array(
    ...
    'capability_type' => 'book',
    // Map read_post, edit_post, etc.
    'map_meta_cap' => true,
    ...
) );

<?php
// Require editors to approve posts:

add_filter( 'map_meta_cap',
function( $required_caps, $cap ) {
    if ( $cap == 'publish_post' || $cap == 'publish_posts' )
        $required_caps[] = 'edit_others_posts';
    return $required_caps;
}, 10, 2 );

<?php
// Don't allow file changes via the UI:

add_filter( 'map_meta_cap',
function( $required_caps, $cap ) {
    if ( in_array( $cap, array(
        'edit_themes',
        'edit_plugins',
        'update_themes',
        'update_plugins',
        'install_themes',
        'install_plugins',
        'update_core' 
        ) ) )
        $required_caps[] = 'do_not_allow';
    return $required_caps;
}, 10, 2 );


// Built into core: (add to wp-config)

// deny edit_themes, edit_plugins
define( 'DISALLOW_FILE_EDIT' true );

// deny all file changes
define( 'DISALLOW_FILE_MODS' true );

<?php
// Only administrators can delete published posts:

add_filter( 'map_meta_cap',
function( $required_caps, $cap ) {
    if ( 'delete_post' == $cap )
        $required_caps[] = 'manage_options';
    return $required_caps;
}, 10, 2 );

<?php
// Don't let anyone delete users:

add_filter( 'map_meta_cap',
function( $required_caps, $cap ) {
    if ( 'delete_user' == $cap || 'delete_users' == $cap )
        $required_caps[] = 'do_not_allow';
    return $required_caps;
}, 10, 2, );

<?php
// Users can edit coments, for 30 minutes:

add_filter( 'map_meta_cap',
function( $caps, $cap, $user_id, $args ) {
    if ( $cap !== 'edit_comment' )
        return $caps;
    $comment_id = $args[1];
    $c = get_comment( $comment_id );
    $user_id = $c->user_id;
    $time = strtotime( $c->comment_date_gmt );
    $window = strtotime( '-30 minutes' );
    if ( $user_id && $time > $window )
        return array(); // No cap required!
    return $caps;
}, 10, 3 );

<?php
// Give secondary "administrators" less control:

add_filter( 'user_has_cap',
function( $caps, $cap, $args ) {
    $user_id = $args[1];
    $user = new WP_User( $user_id );
    $email = $user->user_email;
    if ( $email != get_option('admin_email') )
        $caps['manage_options'] = false;
    return $caps;
}, 10, 3 );

<?php
// If you can edit pages, you can edit widgets

add_filter( 'user_has_cap',
function( $caps ) {
    if ( ! empty( $caps['edit_pages'] ) )
        $caps['edit_theme_options'] = true;
    return $caps;
} );