types.Generator.weakref

Returns a weak reference to the generator.

Return value

A weakref value. Calling its ref() method gives the generator back for as long as something else still holds a strong reference to it; once the generator's refcount drops to zero, ref() returns null instead.

Notes

Takes no arguments. This is a weak reference to the generator value itself. It is unrelated to the reference a suspended generator keeps on its own this. A suspended generator holds every local variable strongly except this, which it holds only weakly, so this reads back as null on the next resume if nothing else has kept it alive:

function body() { yield typeof this; yield typeof this }
let env = {tag = "e"}
let g = body.call(env) // env becomes the generator's 'this'
resume g                // "table" - env is still alive here
env = null               // drop the only other strong reference
resume g                 // "null": this did not survive being suspended

A running generator - between the moment it is resumed and its next yield or return - holds this strongly like any other local.

Example

function geny() { yield 1 }
local g = geny()
let w = g.weakref()
println("typeof w, (w.ref() == g) =", typeof w, w.ref() == g)
g = null
println("w.ref() =", w.ref())

typeof w, (w.ref() == g) = weakref true
w.ref() = null

See also