Merge pull request godotengine#10747 from Calinou/gdscript-typed-dictionaries

Document typed dictionaries in GDScript

Author: skyace65

tutorials/scripting/gdscript/gdscript_basics.rst

@@ -979,6 +979,33 @@ assign to it::
     this, use the :ref:`Object.get() <class_Object_method_get>` and
     :ref:`Object.set() <class_Object_method_set>` methods instead.
 
+Typed dictionaries
+^^^^^^^^^^^^^^^^^^
+
+Godot 4.4 added support for typed dictionaries. On write operations, Godot checks that
+element keys and values match the specified type, so the dictionary cannot contain invalid
+keys or values. The GDScript static analyzer takes typed dictionaries into account. However,
+dictionary methods that return values still have the ``Variant`` return type.
+
+Typed dictionaries have the syntax ``Dictionary[KeyType, ValueType]``, where ``KeyType`` and ``ValueType``
+can be any ``Variant`` type, native or user class, or enum. Both the key and value type **must** be specified,
+but you can use ``Variant`` to make either of them untyped.
+Nested typed collections (like ``Dictionary[String, Dictionary[String, int]]``)
+are not supported.
+
+::
+
+    var a: Dictionary[String, int]
+    var b: Dictionary[String, Node]
+    var c: Dictionary[Vector2i, MyClass]
+    var d: Dictionary[MyEnum, float]
+    # String keys, values can be any type.
+    var e: Dictionary[String, Variant]
+    # Keys can be any type, boolean values.
+    var f: Dictionary[Variant, bool]
+
+``Dictionary`` and ``Dictionary[Variant, Variant]`` are the same thing.
+
 :ref:`Signal <class_Signal>`
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 

tutorials/scripting/gdscript/static_typing.rst

@@ -230,6 +230,35 @@ For instance, you can write::
 The array will remain untyped, but the ``name`` variable within the ``for`` loop
 will always be of ``String`` type.
 
+Specify the element type of a ``Dictionary``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To define the type of a ``Dictionary``'s keys and values, enclose the type name in ``[]``
+and separate the key and value type with a comma.
+
+A dictionary's value type applies to ``for`` loop variables, as well as some operators like
+``[]`` and ``[]=``. Dictionary methods that return values and other operators
+(such as ``==``) are still untyped. Built-in types, native and custom classes,
+and enums may be used as element types. Nested typed collections
+(like ``Dictionary[String, Dictionary[String, int]]``) are not supported.
+
+
+::
+
+    var fruit_costs: Dictionary[String, int] = { "apple": 5, "orange": 10 }
+    var vehicles: Dictionary[String, Node] = { "car": $Car, "plane": $Plane }
+    var item_tiles: Dictionary[Vector2i, Item] = { Vector2i(0, 0): Item.new(), Vector2i(0, 1): Item.new() }
+    var dictionary_of_dictionaries: Dictionary[String, Dictionary] = { { } }
+    # var dicts: Dictionary[String, Dictionary[String, int]] -- disallowed
+
+    for cost in fruit_costs:
+        # cost has type `int`
+
+    # The following would be errors:
+    fruit_costs["pear"] += vehicles
+    var s: String = fruit_costs["apple"]
+    fruit_costs["orange"] = "lots"
+
 Type casting
 ~~~~~~~~~~~~