First of all, make sure that Libraries -> React.xcodeproj -> ThirdParty -> double-conversion
exists and a static library is being produced from it, like this:

Then, if are you're using cocoapods, make sure to add DoubleConversion
to your Podfile
:
target 'MyApp' do
pod 'React', :path => "../node_modules/react-native", :subspecs => [
'Core',
'CxxBridge',
'DevSupport',
# the following ones are the ones taken from "Libraries" in Xcode:
'RCTAnimation',
'RCTActionSheet',
'RCTBlob',
'RCTGeolocation',
'RCTImage',
'RCTLinkingIOS',
'RCTNetwork',
'RCTSettings',
'RCTText',
'RCTVibration',
'RCTWebSocket'
]
pod 'yoga', :path => "../node_modules/react-native/ReactCommon/yoga"
# Here it goes
pod 'DoubleConversion', :podspec => "../node_modules/react-native/third-party-podspecs/DoubleConversion.podspec"
pod 'glog', :podspec => "../node_modules/react-native/third-party-podspecs/glog.podspec"
pod 'Folly', :podspec => "../node_modules/react-native/third-party-podspecs/Folly.podspec"
end
And finally, if none of this worked so far, there's a script you can manually run
in order to resolve React's third-party dependencies.
Just go to node_modules/react-native
and type:
$ ./scripts/ios-install-third-party.sh
Important: Always run it inside node_modules/react-native
. Because, as far as I know, the script uses relative paths in order to store third-party's source code and react native will always look for it at node_modules/react-native/third-party
. So just make sure to run it in the right place.
Note: This script is, probably, already running as a build phase on your project.