title: Resolving CocoaPods child dependency conflict
body: <p>CocoaPods keeps complaining about two dependencies requiring conflicting versions of <code>Protobuf</code>:</p>
  <pre><code>[!] CocoaPods could not find compatible versions for pod &quot;Protobuf&quot;:
    In Podfile:
      flutter_blue (from `.symlinks/plugins/flutter_blue/ios`) was resolved to 0.0.1, which depends on
        flutter_blue/Protos (= 0.0.1) was resolved to 0.0.1, which depends on
          Protobuf (~&gt; 3.11.4)
  
      mobile_scanner (from `.symlinks/plugins/mobile_scanner/ios`) was resolved to 0.0.1, which depends on
        GoogleMLKit/BarcodeScanning (~&gt; 2.6.0) was resolved to 2.6.0, which depends on
          MLKitBarcodeScanning (~&gt; 1.7.0) was resolved to 1.7.0, which depends on
            MLKitVision (~&gt; 3.0) was resolved to 3.0.0, which depends on
              Protobuf (~&gt; 3.12)
  
  There are only pre-release versions available satisfying the following requirements:
  
          'Protobuf', '~&gt; 3.11.4'
  
          'Protobuf', '~&gt; 3.12'
  
  You should explicitly specify the version in order to install a pre-release version
  </code></pre>
  <p>It has a suggestion:</p>
  <pre><code>You should explicitly specify the version in order to install a pre-release version
  </code></pre>
  <p>How do I do that?</p>
  <p>I tried adding</p>
  <pre><code>pod &quot;Protobuf&quot;, &quot;3.12&quot;
  </code></pre>
  <p>But it simply complains again:</p>
  <pre><code>[!] CocoaPods could not find compatible versions for pod &quot;Protobuf&quot;:
    In Podfile:
      Protobuf (= 3.12)
  
      flutter_blue (from `.symlinks/plugins/flutter_blue/ios`) was resolved to 0.0.1, which depends on
        flutter_blue/Protos (= 0.0.1) was resolved to 0.0.1, which depends on
          Protobuf (~&gt; 3.11.4)
  
  Specs satisfying the `Protobuf (= 3.12), Protobuf (~&gt; 3.11.4)` dependency were found, but they required a higher minimum deployment target.
  </code></pre>