Fixing the "Logger" Error in CocoaPods: How to Pin concurrent‑ruby to

When you run npx expo prebuild for your Expo project, it automatically generates the native iOS and Android directories based on your configuration. During the iOS setup, Expo invokes CocoaPods—a Ruby gem that manages native dependencies—to install and configure the required pods. However, this process can sometimes fail when CocoaPods attempts to set up the iOS part of your project.

Specifically, a bug in concurrent‑ruby version 1.3.5, which CocoaPods relies on, causes the installation to break with the following error:

uninitialized constant ActiveSupport::LoggerThreadSafeLevel::Logger (NameError)

Since the iOS setup depends on CocoaPods (and, by extension, on the concurrent‑ruby gem), the workaround is to pin concurrent‑ruby to version 1.3.4. This post will show you, step by step, how to make that adjustment so that your npx expo prebuild command can run successfully.

Step-by-Step Guide to Pin `concurrent‑ruby`

Step 1: Create or Update Your Gemfile

For both macOS and Windows users, a Gemfile is simply a text file that tells Ruby’s package manager, Bundler, which libraries (or "gems") your project needs. In this case, we need to ensure that CocoaPods and the correct version of concurrent‑ruby are installed to avoid the Logger error.

1.1. Ensure Ruby and Bundler Are Installed

For Windows Users:
First, check if Ruby is installed by opening Command Prompt or PowerShell and running:
```
  ruby -v
```
If Ruby isn’t installed, download and install it using RubyInstaller for Windows. Ruby is typically pre-installed on macOS.
For macOS and Windows Users:
Next, check for Bundler by running:
```
  bundle --version
```
If Bundler isn’t installed, install it by running:
```
  gem install bundler
```

1.2. Create or Update Your Gemfile

In the root directory of your project, create (or open) a file named Gemfile and add the following content:

source 'https://rubygems.org'

gem 'cocoapods', '1.16.2'
gem 'concurrent-ruby', '1.3.4'

This configuration tells Bundler to install CocoaPods version 1.16.2 and to pin concurrent‑ruby to version 1.3.4, which avoids the bug causing the Logger error.

Step 2: Install the Dependencies with Bundler

Open your terminal, navigate to your project’s root directory, and run:

bundle install

This command resolves the dependencies and creates a Gemfile.lock file that locks concurrent‑ruby to version 1.3.4, ensuring that this version is used throughout your project.

Step 3: Run Pod Install Using Bundler

Once the dependencies are installed, you need to run CocoaPods to install your iOS dependencies. If you already have an ios directory, navigate to it in your terminal. If you don't have an ios directory yet, let Expo generate it by running:

npx expo prebuild

After the ios directory is generated, navigate into it:

cd ios

Then, run the following command to install the pods using the pinned gems:

bundle exec pod install --repo-update --ansi

Using bundle exec ensures that the pod install process uses the gem versions specified in your Gemfile, which should bypass the Logger error and complete the installation process successfully.

Conclusion

By pinning concurrent‑ruby to version 1.3.4, you avoid the known bug in version 1.3.5 and later, allowing your npx expo prebuild command to complete successfully. This workaround is a quick and effective way to keep your Expo project moving forward while the upstream fix is pending.

Have you encountered this error? Let me know in the comments if this solution worked for you or if you have any other tips to share!

How to Fix the "Logger" Error in CocoaPods by Pinning concurrent‑ruby to 1.3.4

Step-by-Step Guide to Pin concurrent‑ruby