deinit

def deinit[T: Deinitable](var value: T, /)

Extends a value's lifetime up to this call, then deinitializes it.

Mojo deinitializes a value at its last use, not at the end of its enclosing scope. If nothing in the code reads value again after some earlier point, that earlier point is its last use, and its deinitializer runs there. This function is a way to explicitly extend the lifetime of that value until this point exactly.

from std.testing import assert_equal

struct AddOne[origin: MutOrigin]:
    var n: Pointer[Int, Self.origin]

    def __init__(out self, ref[Self.origin] n: Int):
        self.ptr = Pointer(to=n)

    def __deinit__(deinit self):
        self.n[] += 1

def main() raises:
    var n = 0
    var add_one = AddOne(n)
    assert_equal(n, 0)

    # `add_one` is never used, so without the `deinit()` call below, its
    # deinitializer would run immediately after construction, causing
    # `n` to equal `1` and triggering the `assert_equal` to raise an error.
    deinit(add_one^)
    assert_equal(n, 1)

Parameters:

• ​T (Deinitable): The type of the value to destroy. Must conform to Deinitable.

Args:

• ​value (T): The value whose lifetime to extend and then end.