Question

Let’s say I have a method called foo. What’s the difference between:

[self foo];

and

[self performSelector:@selector(foo)];

Are they the same? The first one seems so much easier, so why would you ever want to use the second one?

Answer 1

From the docs:

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];