What is use of performSelector in iOS

Question

What is the role of performSelector?

Comparing:

[self btnClicked];

and

[self performSelector:@selector(btnClicked)];

-(void)btnClicked
{
    NSLog(@"Method Called");
}

both are woking fine for me. What is difference between these two. [self btnClicked] and [self performSelector:@selector(btnClicked)];

Answer 1

The two are pretty identical when used as you have demonstrated, but the latter has the advantage that you can dynamically determine which selector to call at runtime.

SEL selector = [self gimmeASelectorToCall];
[self performSelector: selector];

_[Source]

Answer 2

Apple doc is your friend.

NSObject Protocol Reference

It

Sends a specified message to the receiver and returns the result of the message.

In particular:

The performSelector: method is equivalent to sending an aSelector message directly to the receiver. For example, all three of the following messages do the same thing:

id myClone = [anObject copy];
id myClone = [anObject performSelector:@selector(copy)];
id myClone = [anObject performSelector:sel_getUid("copy")];

However, the performSelector: method allows you to send messages that aren’t determined until runtime. A variable selector can be passed as the argument:

SEL myMethod = findTheAppropriateSelectorForTheCurrentSituation();
[anObject performSelector:myMethod];

The aSelector argument should identify a method that takes no arguments. For methods that return anything other than an object, use NSInvocation.

Hope that helps.