1#@!#!123s

: / proc / self / root / opt / alt / ruby34 / share / ri / system / ObjectSpace / WeakKeyMap /
Filename : cdesc-WeakKeyMap.ri
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U:RDoc::NormalClass[iI"WeakKeyMap:ETI"ObjectSpace::WeakKeyMap;TI"Object;To:RDoc::Markup::Document:@parts[o;;[o:RDoc::Markup::Paragraph;[I"NAn ObjectSpace::WeakKeyMap is a key-value map that holds weak references ;TI"Tto its keys, so they can be garbage collected when there is no more references.;To:RDoc::Markup::BlankLine�o;	;[I"!Unlike ObjectSpace::WeakMap:;T@o:RDoc::Markup::List:
@type:BULLET:@items[o:RDoc::Markup::ListItem:@label0;[o;	;[I"Oreferences to values are _strong_, so they aren't garbage collected while ;TI"they are in the map;;To;;0;[o;	;[I"Ekeys are compared by value (using Object#eql?), not by identity;;To;;0;[o;	;[I":only garbage-collectable objects can be used as keys.;T@o:RDoc::Markup::Verbatim;[I"'map = ObjectSpace::WeakKeyMap.new
;TI"!val = Time.new(2023, 12, 7)
;TI"key = "name"
;TI"map[key] = val
;TI"
;TI"F# Value is fetched by equality: the instance of string "name" is
;TI"2# different here, but it is equal to the key
;TI"/map["name"] #=> 2023-12-07 00:00:00 +0200
;TI"
;TI"val = nil
;TI"GC.start
;TI"A# There are no more references to `val`, yet the pair isn't
;TI"# garbage-collected.
;TI"/map["name"] #=> 2023-12-07 00:00:00 +0200
;TI"
;TI"key = nil
;TI"GC.start
;TI"@# There are no more references to `key`, key and value are
;TI"# garbage-collected.
;TI"map["name"] #=> nil
;T:@format0o;	;[I"R(Note that GC.start is used here only for demonstrational purposes and might ;TI".not always lead to demonstrated results.);T@o;	;[I"VThe collection is especially useful for implementing caches of lightweight value ;TI"Tobjects, so that only one copy of each value representation would be stored in ;TI"Hmemory, but the copies that aren't used would be garbage-collected.;T@o;;[I"%CACHE = ObjectSpace::WeakKeyMap
;TI"
;TI"def make_value(**)
;TI""   val = ValueObject.new(**)
;TI"+   if (existing = @cache.getkey(val))
;TI"@      # if the object with this value exists, we return it
;TI"      existing
;TI"
   else
;TI",      # otherwise, put it in the cache
;TI"      @cache[val] = true
;TI"      val
;TI"   end
;TI"	end
;T;0o;	;[I"[This will result in +make_value+ returning the same object for same set of attributes ;TI"`always, but the values that aren't needed anymore wouldn't be sitting in the cache forever.;T:
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