This is a mob variable (var/mob/usr) containing the mob of the player who executed the current verb, or whose action ultimately called the current proc.
obj/bread
verb/eat()
world << "[usr] eats [src]"If a player named “Bob” calls “eat bread”, the output will be “Bob eats the bread.”
Essentially, usr is an implicit parameter that is passed to every proc or verb. Each procedure inherits the value from its caller. While it can simplify your code in some situations, it can also lead to subtle problems if you are assuming that usr is automatically assigned the value of src when you call a verb programmatically. It is not.
The only time usr is assigned for you is when a player executes a verb, clicks something with the mouse, clicks a link (see Topic), or any other such action.
Note
A good rule of thumb is to never put usr in a proc, only verbs. Typically
usrin a proc is an unsafe programming practice. Ifsrcwould not be the correct choice, it is better to send another argument to your proc with the information it needs.
Certain built-in procs such as Click() are called automatically by a client counterpart like Click(); usually Stat() is called by Stat(); and so on. It is mostly safe to apply usr as directed in those situations, because these procs are pseudo-verbs. It is mostly not safe to apply usr in a movement proc such as Move() or Enter(), because objs and non-player mobs may move autonomously without setting usr.
Although usr is often set in Login() when a client first connects, you should not assume it is valid if Login() is called any other way. Common cases occur when creating a new character, loading a player’s mob from a savefile; or explicitly when setting a mob’s key or changing the value of client.mob. It is safest to use src in mob/Login(), which is always correct, rather than usr.
usr is the default point of reference for several procs like view() and range(), because of their common use in verbs. It is also the default recipient for input() and alert() messages. When using these in procs, be aware of that so you can change the default reference value to something more appropriate.