Unity fails to compile project with firebase analytics because of Cocoapods - ios

Question

I'm trying to integrate Firebase-Analytics in my Unity 2013.3.1 project.
After following the integration guide, I've tried to build the project.
However, Unity fails to build. The reason seems to be cocoapods.
Analyzing dependencies
[!] CocoaPods could not find compatible versions for pod "Firebase/Analytics":
In Podfile:
Firebase/Analytics (= 4.8.1)
None of your spec sources contain a spec satisfying the dependency: `Firebase/Analytics (= 4.8.1)`.
You have either:
* out-of-date source repos which you can update with `pod repo update` or with `pod install --repo-update`.
* mistyped the name or version.
* not added the source repo that hosts the Podspec to your Podfile.
Note: as of CocoaPods 1.0, `pod repo update` does not happen on `pod install` by default.
I've tried to reinstall cocoapods and re-run pod setup, and also deleting the repo and re-setupping using rm -rf ~/.cocoapods/repos/master, but I had no success.
Here's the generated Podfile:
source 'https://github.com/CocoaPods/Specs.git'
platform :ios, '7.0'
target 'Unity-iPhone' do
pod 'Firebase/Analytics', '4.8.1'
pod 'Firebase/Core', '4.8.1'
end
One last thing I've tried was to remove the specific version tags into the Podfile (I've removed the '4.8.1'). This fixed the pod install, however I couldn't find a way to have a successfull build from unity, since the Podfile is auto-generated.
Here's the pod install output after removing the version tag:
Analyzing dependencies
Downloading dependencies
Installing Firebase (4.9.0)
Installing FirebaseAnalytics (4.0.9)
Installing FirebaseCore (4.0.15)
Installing FirebaseInstanceID (2.0.9)
Installing GoogleToolboxForMac (2.1.3)
Installing nanopb (0.3.8)
Generating Pods project
Integrating client project
[!] Please close any current Xcode sessions and use `Unity-iPhone.xcworkspace` for this project from now on.
Sending stats
Pod installation complete! There are 2 dependencies from the Podfile and 6 total pods installed.
It looks like FirebaseAnalytics is currently at version 4.0.9, not 4.8.1.
Did anyone have similar issues?

Answer 1

Update to the 4.4.2 release.
Or to workaround with 4.4.1:
Manually edited each of Dependencies.xml files in Assets/Firebase/Editor to change the version from 4.8.1 to 4.8.2. Example:
<iosPods>
<!-- Mike changed this from 4.8.1 to 4.8.2 -->
<iosPod name="Firebase/Analytics" version="4.8.2" minTargetSdk="7.0">
</iosPod>
</iosPods>
Reference and additional detail here.

Answer 2

The version of FirebaseAnalytics used by Firebase 4.9 is 4.0.9, not 4.8.1. See the podspec for reference.
Another possible issue for failing is that your dependency (iOS 7) is too old and it's not supported by Xcode 9, nor by the latest version of Firebase.
Replace
platform :ios, '7.0'
with
platform :ios, '8.0'