title: Firebase Undefined symbols for architecture x86_64
body: <p>I am using firebase as part of a project I am working on in iOS, and I just stumbled upon the following linking error when I try to compile my code against an iPhone 6 or 7 simulator for testing.</p>
  
  <pre><code>Undefined symbols for architecture x86_64:
    "_OBJC_CLASS_$_GTMSessionUploadFetcher", referenced from:
        objc-class-ref in FirebaseStorage(FIRStorageUploadTask_d5061b1e2b5f1bb249816cc5fc42ff62.o)
    "_OBJC_CLASS_$_GTMLogger", referenced from:
        objc-class-ref in FirebaseMessaging(GIPReachability_ae5504e4a6a28a1d8997c6f38e8bff8b.o)
    "_kGTMSessionUploadFetcherStandardChunkSize", referenced from:
        -[FIRStorageUploadTask enqueue] in FirebaseStorage(FIRStorageUploadTask_d5061b1e2b5f1bb249816cc5fc42ff62.o)
    "_GTMFetcherStandardUserAgentString", referenced from:
        -[FIRAuthBackendRPCIssuerImplementation init] in FirebaseAuth(FIRAuthBackend_ea73237c278bd1b78e1c76db2a16775a.o)
    "_OBJC_CLASS_$_GTMSessionFetcher", referenced from:
        objc-class-ref in FirebaseStorage(FIRStorageDownloadTask_c390366e83519f6636ca985ecb70e5d0.o)
        objc-class-ref in FirebaseStorage(FIRStorage_691ea9ac7cb4d224d37df2ff8a911989.o)
    "_OBJC_CLASS_$_GTMSessionFetcherService", referenced from:
        objc-class-ref in FirebaseAuth(FIRAuthBackend_ea73237c278bd1b78e1c76db2a16775a.o)
        objc-class-ref in FirebaseStorage(FIRStorage_691ea9ac7cb4d224d37df2ff8a911989.o)
  ld: symbol(s) not found for architecture x86_64
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>
  
  <p>I am using Xcode 8.2.1, swift 3.0, and I also have the following Pod file in my project</p>
  
  <pre><code>pod 'Braintree'
  pod 'Firebase/Auth'
  pod 'Firebase/Database'
  pod 'Firebase/Core'
  pod 'Firebase/Storage'
  pod 'Firebase/Messaging'
  pod 'Firebase/RemoteConfig'
  pod 'GeoFire', :git=&gt;'https://github.com/firebase/geofire-objc.git'
  pod 'ObjectMapper', '~&gt; 2.2'
  </code></pre>
  
  <p>I have done a pod update in case something was out of date, but no luck. The code compiles and runs fine when I use an iPhone 4 or 5 simulator.</p>
  
  <p>Edit:</p>
  
  <p>I have set Build Active architectures to No, in valid architectures I have listed arm64, armv7, armv7s and now Objectmapper is failing even though <code>import ObjectMapper</code> is declared in the file</p>
  
  <pre><code> Use of undeclared type 'Mappable'
  </code></pre>
  
  <p>Any help would be greatly appreciated! Thank you in advance.</p>
  
  <p>George.</p>