types.Class.is_frozen

Reports whether this reference to the class was frozen with freeze().

Return value

true if the class is immutable, false otherwise.

Notes

Takes no arguments. The immutable flag lives on the reference, not on the class object: freeze(SomeClass) returns a new, frozen reference to the same class, but a variable that already held that class keeps pointing at an unfrozen reference, and so does every copy made from it before the freeze. SomeClass.is_frozen() stays false unless the variable itself is reassigned to the frozen result, as in SomeClass = freeze(SomeClass).

A frozen class rejects newmember and rawset with trying to modify immutable 'class' and Cannot modify immutable object respectively (the two native paths report it with different text). This is a stronger block than lock(): a locked-but-unfrozen class still accepts new static and function members, while a frozen one rejects every mutation.

Example

class Foo { x = 1 }
println("Foo.is_frozen() before freeze =", Foo.is_frozen())
let frozenFoo = freeze(Foo)
println("frozenFoo.is_frozen() =", frozenFoo.is_frozen())
println("Foo.is_frozen() after freeze =", Foo.is_frozen())

Foo.is_frozen() before freeze = false
frozenFoo.is_frozen() = true
Foo.is_frozen() after freeze = false

See also