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159 lines
7.4 KiB
ReStructuredText
159 lines
7.4 KiB
ReStructuredText
:github_url: hide
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.. _class_Expression:
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Expression
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==========
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**继承：** :ref:`RefCounted<class_RefCounted>` **<** :ref:`Object<class_Object>`
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存储你可以执行的表达式的类。
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.. rst-class:: classref-introduction-group
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描述
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----
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表达式可以由任何算术运算、内置数学函数调用、传递实例的方法调用或内置类型构造调用组成。
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一个使用内置数学函数的示例表达式文本可以是 ``sqrt(pow(3, 2) + pow(4, 2))``\ 。
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在下面的示例中，我们使用 :ref:`LineEdit<class_LineEdit>` 节点来编写表达式并显示结果。
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.. tabs::
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.. code-tab:: gdscript
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var expression = Expression.new()
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func _ready():
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$LineEdit.text_submitted.connect(self._on_text_submitted)
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func _on_text_submitted(command):
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var error = expression.parse(command)
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if error != OK:
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print(expression.get_error_text())
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return
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var result = expression.execute()
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if not expression.has_execute_failed():
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$LineEdit.text = str(result)
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.. code-tab:: csharp
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private Expression _expression = new Expression();
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public override void _Ready()
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{
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GetNode<LineEdit>("LineEdit").TextSubmitted += OnTextEntered;
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}
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private void OnTextEntered(string command)
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{
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Error error = _expression.Parse(command);
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if (error != Error.Ok)
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{
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GD.Print(_expression.GetErrorText());
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return;
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}
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Variant result = _expression.Execute();
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if (!_expression.HasExecuteFailed())
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{
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GetNode<LineEdit>("LineEdit").Text = result.ToString();
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}
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}
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.. rst-class:: classref-introduction-group
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教程
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----
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- :doc:`表达式求值 <../tutorials/scripting/evaluating_expressions>`
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.. rst-class:: classref-reftable-group
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方法
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----
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.. table::
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:widths: auto
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+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
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| :ref:`Variant<class_Variant>` | :ref:`execute<class_Expression_method_execute>`\ (\ inputs\: :ref:`Array<class_Array>` = [], base_instance\: :ref:`Object<class_Object>` = null, show_error\: :ref:`bool<class_bool>` = true, const_calls_only\: :ref:`bool<class_bool>` = false\ ) |
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+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
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| :ref:`String<class_String>` | :ref:`get_error_text<class_Expression_method_get_error_text>`\ (\ ) |const| |
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+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
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| :ref:`bool<class_bool>` | :ref:`has_execute_failed<class_Expression_method_has_execute_failed>`\ (\ ) |const| |
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+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
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| :ref:`Error<enum_@GlobalScope_Error>` | :ref:`parse<class_Expression_method_parse>`\ (\ expression\: :ref:`String<class_String>`, input_names\: :ref:`PackedStringArray<class_PackedStringArray>` = PackedStringArray()\ ) |
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+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
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.. rst-class:: classref-section-separator
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----
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.. rst-class:: classref-descriptions-group
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方法说明
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--------
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.. _class_Expression_method_execute:
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.. rst-class:: classref-method
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:ref:`Variant<class_Variant>` **execute**\ (\ inputs\: :ref:`Array<class_Array>` = [], base_instance\: :ref:`Object<class_Object>` = null, show_error\: :ref:`bool<class_bool>` = true, const_calls_only\: :ref:`bool<class_bool>` = false\ ) :ref:`🔗<class_Expression_method_execute>`
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执行之前由 :ref:`parse()<class_Expression_method_parse>` 解析的表达式，并返回结果。在使用返回的对象之前，应该通过调用 :ref:`has_execute_failed()<class_Expression_method_has_execute_failed>` 来检查方法是否失败。
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如果你在 :ref:`parse()<class_Expression_method_parse>` 中定义了输入变量，你可以在输入数组中以同样的顺序指定它们的值。
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.. rst-class:: classref-item-separator
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----
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.. _class_Expression_method_get_error_text:
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.. rst-class:: classref-method
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:ref:`String<class_String>` **get_error_text**\ (\ ) |const| :ref:`🔗<class_Expression_method_get_error_text>`
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如果 :ref:`parse()<class_Expression_method_parse>` 或 :ref:`execute()<class_Expression_method_execute>` 失败，则返回错误文本。
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.. rst-class:: classref-item-separator
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----
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.. _class_Expression_method_has_execute_failed:
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.. rst-class:: classref-method
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:ref:`bool<class_bool>` **has_execute_failed**\ (\ ) |const| :ref:`🔗<class_Expression_method_has_execute_failed>`
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如果 :ref:`execute()<class_Expression_method_execute>` 失败，返回 ``true``\ 。
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.. rst-class:: classref-item-separator
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----
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.. _class_Expression_method_parse:
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.. rst-class:: classref-method
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:ref:`Error<enum_@GlobalScope_Error>` **parse**\ (\ expression\: :ref:`String<class_String>`, input_names\: :ref:`PackedStringArray<class_PackedStringArray>` = PackedStringArray()\ ) :ref:`🔗<class_Expression_method_parse>`
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解析表达式并返回 :ref:`Error<enum_@GlobalScope_Error>` 代码。
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你也可以选择用 ``input_names`` 来指定可能出现在表达式中的变量名称，这样就可以在执行表达式时进行绑定。
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.. |virtual| replace:: :abbr:`virtual (本方法通常需要用户覆盖才能生效。)`
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.. |required| replace:: :abbr:`required (This method is required to be overridden when extending its base class.)`
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.. |const| replace:: :abbr:`const (本方法无副作用，不会修改该实例的任何成员变量。)`
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.. |vararg| replace:: :abbr:`vararg (本方法除了能接受在此处描述的参数外，还能够继续接受任意数量的参数。)`
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.. |constructor| replace:: :abbr:`constructor (本方法用于构造某个类型。)`
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.. |static| replace:: :abbr:`static (调用本方法无需实例，可直接使用类名进行调用。)`
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.. |operator| replace:: :abbr:`operator (本方法描述的是使用本类型作为左操作数的有效运算符。)`
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.. |bitfield| replace:: :abbr:`BitField (这个值是由下列位标志构成位掩码的整数。)`
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.. |void| replace:: :abbr:`void (无返回值。)`
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