what is the way to calling a library in object oriented style?

Any autoloader can be loaded by setting $config['composer_autoload'] to a custom path in application/config/config.php. The path just has to point to a script which will register the autoloader (like Composer's vendor/autoload.php script). This is called before the Hooks class is loaded, so the only way to get an autoloader registered any earlier would be to register it in index.php or modify the CI code (or something odd like register it in a config file).

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