types.Instance.rawset

Method on every instance

instance.rawset(key, value): any

Replaces the value stored at an existing field of this instance, without consulting a _newslot metamethod.

The binding carries no declaration string, so the VM cannot report parameter names. The names above are from this page; the types and attributes still come from the VM. The VM also cannot tell an optional parameter from a variadic tail here, so read the brackets and any trailing ... from the prose below, not from the signature.

Parameters

`key`	any	the field name to update
`value`	any	the value to store there

Return value

The instance itself, so calls can be chained.

Errors

Throws the index '<key>' (type='<type>') does not exist if key is not already a field of the instance. Unlike a table or an unlocked class, an instance can never gain a new slot this way - the language reference states instance members cannot be removed, and the same restriction covers adding one. Attempting to rawset a method name fails the same way: a method is not a per-instance value slot to overwrite. On a frozen reference, throws Cannot modify immutable object.

Notes

Use rawset when the instance's class defines a _newslot metamethod and the plain (non-raw) assignment should not trigger it.

Example

examples/types/instance/rawset.nut

class Foo { x = 1 }
let f = Foo()
let same = f.rawset("x", 42)
println("same == f =", same == f, "f.x =", f.x)
try {
  f.rawset("newkey", 1)
} catch (e) {
  println("f.rawset(\"newkey\", 1) throws:", e)
}

Output:

same == f = true f.x = 42
f.rawset("newkey", 1) throws: the index 'newkey' (type='string') does not exist