An ObjectSpace::WeakMap is a key-value map that holds weak references to its keys and values, so they can be garbage-collected when there are no more references left.
Keys in the map are compared by identity.
m = ObjectSpace::WeakMap.new key1 = "foo" val1 = Object.new m[key1] = val1 key2 = "foo" val2 = Object.new m[key2] = val2 m[key1] #=> #<Object:0x0...> m[key2] #=> #<Object:0x0...> val1 = nil # remove the other reference to value GC.start m[key1] #=> nil m.keys #=> ["bar"] key2 = nil # remove the other reference to key GC.start m[key2] #=> nil m.keys #=> []
(Note that GC.start is used here only for demonstrational purposes and might not always lead to demonstrated results.)
See also ObjectSpace::WeakKeyMap map class, which compares keys by value, and holds weak references only to the keys.
static VALUE
wmap_aref(VALUE self, VALUE key)
{
VALUE obj = wmap_lookup(self, key);
return !UNDEF_P(obj) ? obj : Qnil;
}
Returns the value associated with the given key if found.
If key is not found, returns nil.
static VALUE
wmap_aset(VALUE self, VALUE key, VALUE val)
{
struct weakmap *w;
TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
VALUE pair[2] = { key, val };
st_update(w->table, (st_data_t)pair, wmap_aset_replace, (st_data_t)pair);
RB_OBJ_WRITTEN(self, Qundef, key);
RB_OBJ_WRITTEN(self, Qundef, val);
return nonspecial_obj_id(val);
}
Associates the given value with the given key.
If the given key exists, replaces its value with the given value; the ordering is not affected.
static VALUE
wmap_delete(VALUE self, VALUE key)
{
struct weakmap *w;
TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
VALUE orig_key = key;
st_data_t orig_key_data = (st_data_t)&orig_key;
st_data_t orig_val_data;
if (st_delete(w->table, &orig_key_data, &orig_val_data)) {
VALUE orig_val = *(VALUE *)orig_val_data;
rb_gc_remove_weak(self, (VALUE *)orig_key_data);
rb_gc_remove_weak(self, (VALUE *)orig_val_data);
wmap_free_entry((VALUE *)orig_key_data, (VALUE *)orig_val_data);
if (wmap_live_p(orig_val)) {
return orig_val;
}
}
if (rb_block_given_p()) {
return rb_yield(key);
}
else {
return Qnil;
}
}
Deletes the entry for the given key and returns its associated value.
If no block is given and key is found, deletes the entry and returns the associated value:
m = ObjectSpace::WeakMap.new key = "foo" m[key] = 1 m.delete(key) # => 1 m[key] # => nil
If no block is given and key is not found, returns nil.
If a block is given and key is found, ignores the block, deletes the entry, and returns the associated value:
m = ObjectSpace::WeakMap.new key = "foo" m[key] = 2 m.delete(key) { |key| raise 'Will never happen'} # => 2
If a block is given and key is not found, yields the key to the block and returns the block’s return value:
m = ObjectSpace::WeakMap.new m.delete("nosuch") { |key| "Key #{key} not found" } # => "Key nosuch not found"
static VALUE
wmap_each(VALUE self)
{
struct weakmap *w;
TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
wmap_foreach(w, wmap_each_i, (st_data_t)0);
return self;
}
Iterates over keys and values. Note that unlike other collections, each without block isn’t supported.
static VALUE
wmap_each_key(VALUE self)
{
struct weakmap *w;
TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
wmap_foreach(w, wmap_each_key_i, (st_data_t)0);
return self;
}
Iterates over keys. Note that unlike other collections, each_key without block isn’t supported.
static VALUE
wmap_each_value(VALUE self)
{
struct weakmap *w;
TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
wmap_foreach(w, wmap_each_value_i, (st_data_t)0);
return self;
}
Iterates over values. Note that unlike other collections, each_value without block isn’t supported.
static VALUE
wmap_has_key(VALUE self, VALUE key)
{
return RBOOL(!UNDEF_P(wmap_lookup(self, key)));
}
Returns true if key is a key in self, otherwise false.
static VALUE
wmap_inspect(VALUE self)
{
VALUE c = rb_class_name(CLASS_OF(self));
struct weakmap *w;
TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
VALUE str = rb_sprintf("-<%"PRIsVALUE":%p", c, (void *)self);
wmap_foreach(w, wmap_inspect_i, (st_data_t)str);
RSTRING_PTR(str)[0] = '#';
rb_str_cat2(str, ">");
return str;
}
static VALUE
wmap_keys(VALUE self)
{
struct weakmap *w;
TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
VALUE ary = rb_ary_new();
wmap_foreach(w, wmap_keys_i, (st_data_t)ary);
return ary;
}
Returns a new Array containing all keys in the map.
static VALUE
wmap_size(VALUE self)
{
struct weakmap *w;
TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
st_index_t n = st_table_size(w->table);
#if SIZEOF_ST_INDEX_T <= SIZEOF_LONG
return ULONG2NUM(n);
#else
return ULL2NUM(n);
#endif
}
Returns the number of referenced objects
static VALUE
wmap_values(VALUE self)
{
struct weakmap *w;
TypedData_Get_Struct(self, struct weakmap, &weakmap_type, w);
VALUE ary = rb_ary_new();
wmap_foreach(w, wmap_values_i, (st_data_t)ary);
return ary;
}
Returns a new Array containing all values in the map.