If you do not determine the version of iOS, 4.3 is considered the default cocoapods
For example, if you define a Podfile as shown below platform :ios, '5.0' , the minimum version of iOS for your file will be 5.0
In your case, this means that Nimbus has a higher iOS version number, defined as the minimum in its podspec. Update your subfile to support a higher version depending on your minimum project goal or check if previous versions of Nimbus are compatible with ios 4.3
to determine the specific version to use pod pod 'Nimbus', '0.X.Y' , where X and Y are version numbers
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