isobj

isobj <object>

Whether an object reference still names a live object.

This is the object-specific liveness check: it is true when the argument is an object reference whose object is still in the world, and false when that object has since been extracted (a stale reference).

The argument must actually be an object: passing null or a value of another type is a run-time error, not a clean false. To test a value that might be null — for example the result of first on an empty iterable — use exists or isnull, which accept any value.

Arguments

Returns

A bool — true if the reference names a live object, false if it is stale.

Examples

after command (say) {
  oload 1
  let item [first [inventory $self]]
  do "say isobj=[isobj $item]."
}

After oload places an object (vnum 1) into the owner's inventory, first of the inventory yields that object, so [isobj $item] is true.

after command (say) {
  let item [first [inventory $self]]
  if [exists $item] {
    do "say isobj=[isobj $item]."
  }
}

Guard with exists first, since first may return null and isobj errors on a null argument. When something is carried, item is a live object and [isobj $item] is true.

See also