How can I resolve the 'FIRVectorValue' undeclared identifier error in Flutter Cloud Firestore on iOS?

Below is one common cause and a few steps to resolve your build issues.

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What’s Happening

The error

  Use of undeclared identifier 'FIRVectorValue'

in FLTFirebaseFirestoreReader.m suggests that the Cloud Firestore plugin’s native code is referencing a symbol from the Firebase iOS SDK that isn’t available in your current dependency setup. Often this happens when there’s a mismatch between the versions of Firebase iOS SDK components that the Flutter plugins expect and what is actually installed via CocoaPods.

The CodeSign error is typically a follow‑on failure when the build process aborts due to a compilation error.

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Resolution Steps

1. Ensure Consistent Firebase Versions

   • Verify that all Firebase-related Flutter plugins are using compatible versions. In your case, the pubspec.yaml declares versions such as:

   YAMLCopied
     cloud_firestore: ^5.0.0
     firebase_auth: ^5.4.1
     google_sign_in: ^6.1.6
     firebase_storage: ^12.4.1
     firebase_core: ^3.10.1

   Although you declared a minimum version for cloud_firestore (^5.0.0), the package actually being used (as seen in the error path) is 5.6.2. Sometimes newer versions of the plugin may require an updated Firebase iOS SDK. Make sure that all plugins pull in compatible Firebase iOS SDK versions.

2. Update CocoaPods Repositories and Install Pods

   • In your iOS project folder, run:

     BASHCopied
     pod repo update
     pod install --repo-update

   This ensures that you’re getting the latest podspecs and that Firebase iOS pods are updated.

3. Clean the Build Artifacts

   • Remove derived data from Xcode and clean the build folder (Product > Clean Build Folder). Alternatively, you can delete the Pods folder and Podfile.lock and then run pod install again.

4. Set the Minimum iOS Deployment Target

   • Open your Podfile and check that the platform is set to at least iOS 10 or higher:

     RUBYCopied
     platform :ios, '10.0'

   Some Firebase iOS SDK components require a minimum target version.

5. Rebuild the Project

   Once the pods are updated and the iOS platform is correct, try rebuilding the project in Xcode. The symbol should now be available if the correct Firebase iOS SDK version is installed.

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Why This Matters

Firebase plugins for Flutter (and especially for Cloud Firestore) bundle native code that expects specific symbols. If the underlying Firebase iOS SDK isn’t updated—or if different Firebase pods are out of sync—the compiler won’t find symbols like FIRVectorValue. Updating your pods and ensuring that your Podfile and deployment targets align with Firebase’s requirements usually resolves the issue.

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Following the above steps usually resolves the “undeclared identifier 'FIRVectorValue'” error and the subsequent CodeSign build failure.