What is double star (eg. NSError **)?

Question

So, I saw this:

error:(NSError **)error

in the apple doc\'s. Why two stars? What is the significance?

Answer 1

In C everything is pass by value. If you want to change the value of something you pass the address of it (which passes the value of the memory address). If you want to change where a pointer points you pass the the addres of the pointer.

Take a look here for a simple explanation.