add_menu_page does not seem to work in a class

Question

Here is some of my code:

class proposal {

function __construct() {
    add_menu_page('Topic Proposal', 'Topic Proposal', 'read', 'topic_proposal', array(&$this, 'writer_page'), 'dashicons-welcome-add-page');
}

public function load_menu() {
    echo 'EHY';
}

public function writer_page() {
    ?>
        <h1>Topic Proposal</h1>
    <?php
}

public function editor_page() {
    ?>
        <h1>Topic Proposal</h1>
    <?php
}

}

add_action( 'admin_init', function(){return new proposal();});

The "Topic Proposal" shows of on the menu but when I click on it I get this:

You do not have sufficient permissions to access this page.

What am I doing wrong?

Answer 1

From add_menu_page in Codex:

Note: If you're running into the "You do not have sufficient permissions to access this page" error, then you've hooked too early. The hook you should use is admin_menu.

admin_init is too early to hook add_menu_page, use admin_menu.