godot/doc/classes/Expression.xml

<?xml version="1.0" encoding="UTF-8" ?>
<class name="Expression" inherits="RefCounted" version="4.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
	<brief_description>
		A class that stores an expression you can execute.
	</brief_description>
	<description>
		An expression can be made of any arithmetic operation, built-in math function call, method call of a passed instance, or built-in type construction call.
		An example expression text using the built-in math functions could be [code]sqrt(pow(3, 2) + pow(4, 2))[/code].
		In the following example we use a [LineEdit] node to write our expression and show the result.
		[codeblocks]
		[gdscript]
		var expression = Expression.new()

		func _ready():
		    $LineEdit.text_submitted.connect(self._on_text_submitted)

		func _on_text_submitted(command):
		    var error = expression.parse(command)
		    if error != OK:
		        print(expression.get_error_text())
		        return
		    var result = expression.execute()
		    if not expression.has_execute_failed():
		        $LineEdit.text = str(result)
		[/gdscript]
		[csharp]
		private Expression _expression = new Expression();

		public override void _Ready()
		{
		    GetNode&lt;LineEdit&gt;("LineEdit").TextSubmitted += OnTextEntered;
		}

		private void OnTextEntered(string command)
		{
		    Error error = _expression.Parse(command);
		    if (error != Error.Ok)
		    {
		        GD.Print(_expression.GetErrorText());
		        return;
		    }
		    Variant result = _expression.Execute();
		    if (!_expression.HasExecuteFailed())
		    {
		        GetNode&lt;LineEdit&gt;("LineEdit").Text = result.ToString();
		    }
		}
		[/csharp]
		[/codeblocks]
	</description>
	<tutorials>
		<link title="Evaluating Expressions">$DOCS_URL/tutorials/scripting/evaluating_expressions.html</link>
	</tutorials>
	<methods>
		<method name="execute">
			<return type="Variant" />
			<param index="0" name="inputs" type="Array" default="[]" />
			<param index="1" name="base_instance" type="Object" default="null" />
			<param index="2" name="show_error" type="bool" default="true" />
			<param index="3" name="const_calls_only" type="bool" default="false" />
			<description>
				Executes the expression that was previously parsed by [method parse] and returns the result. Before you use the returned object, you should check if the method failed by calling [method has_execute_failed].
				If you defined input variables in [method parse], you can specify their values in the inputs array, in the same order.
			</description>
		</method>
		<method name="get_error_text" qualifiers="const">
			<return type="String" />
			<description>
				Returns the error text if [method parse] or [method execute] has failed.
			</description>
		</method>
		<method name="has_execute_failed" qualifiers="const">
			<return type="bool" />
			<description>
				Returns [code]true[/code] if [method execute] has failed.
			</description>
		</method>
		<method name="parse">
			<return type="int" enum="Error" />
			<param index="0" name="expression" type="String" />
			<param index="1" name="input_names" type="PackedStringArray" default="PackedStringArray()" />
			<description>
				Parses the expression and returns an [enum Error] code.
				You can optionally specify names of variables that may appear in the expression with [param input_names], so that you can bind them when it gets executed.
			</description>
		</method>
	</methods>
</class>