CODEWITHSUNDEEP
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user236739
user236739

Reputation: 1323

iOS - Ensure execution on main thread

I want to know how to call my function on the main thread.

How do I make sure my function is called on the main thread?

(this follows a previous question of mine).

Upvotes: 74

Views: 116907

Answers (4)

shoughton123
shoughton123

Reputation: 4251

This will do it:

[[NSOperationQueue mainQueue] addOperationWithBlock:^ {

   //Your code goes in here
   NSLog(@"Main Thread Code");

}];

Upvotes: 168

CarlJ
CarlJ

Reputation: 9481

When you're using iOS >= 4

dispatch_async(dispatch_get_main_queue(), ^{
  //Your main thread code goes in here
  NSLog(@"Im on the main thread");       
});

Upvotes: 139

Sean Danzeiser
Sean Danzeiser

Reputation: 9243

i think this is cool, even tho in general its good form to leave the caller of a method responsible for ensuring its called on the right thread.

if (![[NSThread currentThread] isMainThread]) {
    [self performSelector:_cmd onThread:[NSThread mainThread] withObject:someObject waitUntilDone:NO];
    return;
}

Upvotes: 12

Amy Worrall
Amy Worrall

Reputation: 16337

there any rule I can follow to be sure that my app executes my own code just in the main thread?

Typically you wouldn't need to do anything to ensure this — your list of things is usually enough. Unless you're interacting with some API that happens to spawn a thread and run your code in the background, you'll be running on the main thread.

If you want to be really sure, you can do things like

[self performSelectorOnMainThread:@selector(myMethod:) withObject:anObj waitUntilDone:YES];

to execute a method on the main thread. (There's a GCD equivalent too.)

Upvotes: 49

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