Set viewController shared public object - c++

Question

I've got ViewController that contains tableView and an array of items to be displayed on that table.
In order to change table content, I could initialise the array and calling reloadData method from within ViewController button callback (see buttonTap method below).
However, I also need to change the table contents from external code outside the scope of viewController, but it's inaccessible.
In the minimal example below I'm using external C/C++ based thread that unsuccessfully attempts to access a viewController method but it fails on compilation due to No known class method for selector 'changeArr'
Any idea how to make viewController public ?
viewController.m
#import "ViewController.h"
#interface ViewController() <NSTableViewDelegate, NSTableViewDataSource>
#property (weak) IBOutlet NSTableView *tableView;
#property NSMutableArray<NSString*> * arr;
#end
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.tableView.delegate = self;
self.tableView.dataSource = self;
[self.tableView reloadData];
}
- (void)viewWillAppear {
[super viewWillAppear];
[self.tableView reloadData];
}
- (NSInteger)numberOfRowsInTableView:(NSTableView *)tableView {
return self.arr.count;
}
- (NSView *)tableView:(NSTableView *)tableView viewForTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row {
NSTableCellView* cellView =(NSTableCellView*)[tableView makeViewWithIdentifier:#"cell1" owner:nil];
cellView.textField.stringValue = self.arr[row];
return cellView;
}
-(void)changeArr {
self.arr = [NSMutableArray arrayWithObjects:#"ccc", #"ddd", nil];
[self.tableView reloadData];
NSLog(#"fwefwe");
}
- (IBAction)buttonTap:(id)sender {
self.arr = [NSMutableArray arrayWithObjects:#"AAAA", #"BBB", nil];
[self.tableView reloadData];
}
main.m
#import <Cocoa/Cocoa.h>
#include <pthread.h>
#import "ViewController.h"
void updateTable() {
sleep(10);
dispatch_sync(dispatch_get_main_queue(), ^{ [ViewController changeArr]; }); // ERROR : No known class method for selector 'changeArr'
}
int main(int argc, const char * argv[]) {
#autoreleasepool {
// Setup code that might create autoreleased objects goes here.
}
pthread_t threadHandler;
pthread_create(&threadHandler, NULL, &updateTable, NULL);
return NSApplicationMain(argc, argv);
}

Answer 1

changeArr is a private function(-). So you can't call [ViewController changeArr].
If you change changeArr to public fuction(+), it's impossible to access internal array.
So I think the easy way to do this task is using a instance of ViewController by singletone.
...
#implementation ViewController
+ (id) sharedViewController {
static ViewController *sharedInstance = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
UIStoryboard *storyboard = [UIStoryboard storyboardWithName:#"MainStoryboard" bundle:nil];
sharedInstance = [storyboard instantiateViewControllerWithIdentifier:#"MyViewControllerIdentifier"];
});
return sharedInstance ;
}
- (void)viewDidLoad {
[super viewDidLoad];
...
and in updateTable:
dispatch_sync(dispatch_get_main_queue(), ^{ [[ViewController sharedViewController] changeArr]; });