What exactly is super in Objective-C?

Question

As far as I know, it's a pointer to the superclass. It's hard-wired with the superclass, and not dynamically figured out at runtime. Would like to know it more in detail...

Anyone?

Hayne

Answer 1

super

Essentially, it allows you to use the implementations of the current class' superclass.

For the gritty details of the Objective-C runtime:

[super message] has the following meaning:

When it encounters a method call, the compiler generates a call to one of the functions objc_msgSend, objc_msgSend_stret, objc_msgSendSuper, or objc_msgSendSuper_stret. Messages sent to an object’s superclass (using the super keyword) are sent using objc_msgSendSuper; other messages are sent using objc_msgSend. Methods that have data structures as return values are sent using objc_msgSendSuper_stret and objc_msgSend_stret.

So yes, it is static, and not determined at runtime.

Scalenus

Possibly cause for a new question, but super behaves oddly (or "normally", if you think that way) in categories. That is, it treats the category as a subclass (not an override), so super is then the original, unmodified class. Sort of. Sometimes. "It's complicated." – Precedent

"gritty" "details" - links are dead – Gaiseric

Answer 2

It's a keyword that's equivalent to self, but starts its message dispatch searching with the superclass's method table.

Piquet

Answer 3

super is not a pointer to a class. Super is self, but when used in a message expression, it means "look for an implementation starting with the superclass's method table."

Selfservice

This is not true for class methods. – Richly

Answer 4

These blog postings on what is a meta class?, getting subclasses and classes and metaclasses may give you some insight on the internals of this.

Phototaxis