How can I regenerate ios folder in React Native project?

The process you need to follow is so similar to renaming a react native app. Basically you just need to run react-native upgrade in your root project directory. For further info you can check another question here. The instructions below explains how to create another react native project based on a copied one with a new name.

• First copy the directory which your to-be-name-changed application exists. And go to your newly cloned directory.
• Change the name at index.ios/android.js file which is given as a parameter to AppRegistry.
• Change the name and version accordingly on package.json
• Delete /ios and /android folders which are remaining from your older app.
• Run $react-native upgrade to generate /ios and /android folders again.
• Run $react-native link for any native dependency.
• Finally run $react-native run-ios or anything you want.