Q:

'RCTViewManager.h' file not found

I'm trying to implement Native UI Components https://facebook.github.io/react-native/docs/native-components-ios.html and when I try to create the following file in Xcode
// RCTMapManager.m
#import <MapKit/MapKit.h>

#import "RCTViewManager.h"

@interface RCTMapManager : RCTViewManager
@end

@implementation RCTMapManager

RCT_EXPORT_MODULE()

- (UIView *)view
{
  return [[MKMapView alloc] init];
}

@end

I get the following error 

RCTMapManager.m:3:9: 'RCTViewManager.h' file not found

Then I tried to add the following path to the Header Search Path

$(SRCROOT)/../node_modules/react-native/React/**

The previous compilation error is gone but I get the following error when I run the project

2 duplicate symbols for architecture x86_64 clang: error: linker
  command failed with exit code 1 (use -v to see invocation)

Any idea ??

A:

I've found the solution to my problem. 
Basically there're two problems. First the import should be from "React/RCTViewManager.h" instead of "RCTViewManager".
Second, the class should not be named "RCTMapManager" as this class already exists. It should be named something else (e.g. "RNTMapManager"). 
Details could be found on the following github issue https://github.com/facebook/react-native/issues/12404 and documentation was fixed with this pull request https://github.com/facebook/react-native/pull/12523

