Basic Native UI component Bridging Code

AccessReactSubView.m

//RCTListViewManger.h

#import <UIKit/UIKit.h>

@interface RCTNativeListView : UIView
@property (nonatomic) NSArray * colors;

@end
--------------------------------------------------------------------------------
//RCTListViewManger.m
#import "RCTNativeListView.h"
#import "UIView+React.h"


@implementation RCTNativeListView



- (instancetype)init {
  NSLog(@"init");
  self = [super init];
  if ( self ) {
    [self setUp];
  }
  return self;
}

- (instancetype)initWithFrame:(CGRect)frame
{
  self = [super initWithFrame:frame];
  return self;
}

- (instancetype)initWithCoder:(NSCoder *)coder
{
  self = [super initWithCoder:coder];
  return self;
}

- (void) insertReactSubview:(UIView *)subview atIndex:(NSInteger)atIndex {
  NSLog(@"insde");
  [super insertReactSubview:subview atIndex:atIndex];
}

- (void)setUp {
  UIView * sampleView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
  sampleView.backgroundColor = [UIColor blackColor];
  [self addSubview:sampleView];
}

@end
-------------------------------------------------------------------------------- 
  
// RCTListViewManger.h
#import "RCTViewManager.h"
#import "RCTNativeListView.h"

@interface RCTNativeListViewManager : RCTViewManager

@property (nonatomic) RCTNativeListView * nativeListView;

@end
--------------------------------------------------------------------------------
  
// RCTListViewManger.m
#import "RCTNativeListViewManager.h"

@implementation RCTNativeListViewManager

RCT_EXPORT_MODULE()

- (instancetype)init {
  self = [super init];
  if ( self ) {
    NSLog(@"color picker manager init");
    self.nativeListView = [[RCTNativeListView alloc] init];
  }
  return self;
}


- (UIView *)view {
  NSLog(@"color picker manager -view method");
  return self.nativeListView;
}

@end

Objective guildline

1)Create a ViewManager and View Class
2)Create A UIView instants (desired one) and its wrapper(again a UIView instance) Line - 45
3)override the insertReactSubviews method line - 40

NativelistView.js

<NativeListView style={{ flex: 1 }}>
       <View style={{ height: 50, width: 50, backgroundColor: 'red' }} />
 </NativeListView>

output