Expression

继承： RefCounted < Object

A class that stores an expression you can execute.

描述

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 sqrt(pow(3, 2) + pow(4, 2)).

In the following example we use a LineEdit node to write our expression and show the result.

    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)

    private Expression _expression = new Expression();
    
    public override void _Ready()
    {
        GetNode<LineEdit>("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<LineEdit>("LineEdit").Text = result.ToString();
        }
    }

方法

方法说明

Variant execute ( inputs: Array = [], base_instance: Object = null, show_error: bool = true, const_calls_only: bool = false )

Executes the expression that was previously parsed by parse and returns the result. Before you use the returned object, you should check if the method failed by calling has_execute_failed.

If you defined input variables in parse, you can specify their values in the inputs array, in the same order.

String get_error_text ( ) const¹

Returns the error text if parse or execute has failed.

bool has_execute_failed ( ) const¹

Returns true if execute has failed.

Error parse ( expression: String, input_names: PackedStringArray = PackedStringArray() )

Parses the expression and returns an Error code.

You can optionally specify names of variables that may appear in the expression with input_names, so that you can bind them when it gets executed.