ObjectSpace::WeakKeyMap#getkey

(untyped) -> Key?

map.getkey(key) → existing_key or nil

static VALUE
wkmap_getkey(VALUE self, VALUE key)
{
    struct weakkeymap *w;
    TypedData_Get_Struct(self, struct weakkeymap, &weakkeymap_type, w);

    st_data_t orig_key;
    if (!st_get_key(w->table, (st_data_t)&key, &orig_key)) return Qnil;

    return *(VALUE *)orig_key;
}

Returns the existing equal key if it exists, otherwise returns nil.

This might be useful for implementing caches, so that only one copy of some object would be used everywhere in the program:

Example

value = {amount: 1, currency: 'USD'}

# Now if we put this object in a cache:
cache = ObjectSpace::WeakKeyMap.new
cache[value] = true

# ...we can always extract from there and use the same object:
copy = cache.getkey({amount: 1, currency: 'USD'})
copy.object_id == value.object_id #=> true

See also #delete #inspect #clear #key? also in 4.1 · 4.0 · 3.3

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