dev/integration_tests/ios_host_app/Host/ViewController.m

#import "ViewController.h"
#import <Flutter/Flutter.h>
#import <FlutterPluginRegistrant/GeneratedPluginRegistrant.h>

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    [button addTarget:self
               action:@selector(handleButtonAction)
     forControlEvents:UIControlEventTouchUpInside];
    [button setTitle:@"Press me" forState:UIControlStateNormal];
    [button setBackgroundColor:[UIColor blueColor]];
    button.frame = CGRectMake(80.0, 210.0, 160.0, 40.0);
    [self.view addSubview:button];
}

- (void)handleButtonAction {
    FlutterViewController* flutterViewController = [[FlutterViewController alloc] init];
    [GeneratedPluginRegistrant registerWithRegistry:flutterViewController];
    [self presentViewController:flutterViewController animated:false completion:nil];
}

@end