Format
&A
Returns
A pointer to the var or list item A.
This operator is also called the reference operator, since it creates a reference to a var that you can use elsewhere.)
Sometimes it is desirable to have easy access to a var without knowing its name, or send multiple items back from a proc. To do this, you can create a pointer to that var. Then you can use the * operator to refer to the value inside the pointer, or even to assign a value to it.
var/a=3, b=4
var/p = &a
world << *p // same as world << a
*p = 5 // same as a = 5
var/list/L = list(1, 2, 3)
var/list/pl = &L[2]
*pl *= 10 // same as L[2] *= 10If you want the compiler to recognize that the item in your pointer var should be a certain type, you can give the pointer var that same type. Hence in the example above, pl is defined as a /list.
You can also call procs this way. You can either wrap the pointer and the * operator in paretheses, like (*p).MyProc(), or you can skip the operator and just call p.MyProc() directly.
The same also applies to the list index operator []. If p = &list then you can use (*p)[index] or p[index] interchangeably.
Pointers can be made for any of these kinds of vars:
- Vars belonging to an object
- Local vars in a proc, including
src,usr, and the.var - Arguments in a proc
- Global vars
- An item in a list, including values in associative lists
One advantage of pointers is that you can use them to alter a value in a suspended (sleeping) proc.
Note
When spawn() is used, the current proc is forked, where one keeps running and a copy is scheduled to run later. If any pointers to proc vars were created, they belong to the original proc (the one that keeps running), not to the fork.