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Attention | Topic was automatically imported from the old Question2Answer platform. |
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Asked By | Alexandr |
hello, is it possible to make the code from the string be activated?
example:
var s = “variable + = 1”
dynamic (s)
or
var variable = 10
var s = “print(variable)”
dynamic(s)
** output **
10
like that
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Reply From: | flurick |
Yes! https://twitter.com/reduzio/status/1027293084844019713
var e = Expression.new()
e.parse( "1+2")
print(e.execute())
Wow you ninja’d me! I’ve heard about this feature but I didn’t think it has been implemented.
Xrayez | 2018-10-16 18:41
This work in 3.0.6?
Alexandr | 2018-10-16 19:01
This works in 3.1 alpha at least.
Xrayez | 2018-10-17 08:00
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Reply From: | Xrayez |
You can create scripts dynamically. I scratched my head a bit and figured this silly example, but should give you an idea:
extends Node2D
var variable = 0
func _ready():
var expression = "variable += 1"
var result = execute(expression)
print(result) # should print 1
func execute(p_expression):
assert(typeof(p_expression) == TYPE_STRING)
# Create a new script with embedded expression
var script = GDScript.new()
# Define source code needed for evaluation (extends Reference by default)
script.source_code += \
"""
var variable = %s
func eval():
%s
return variable
""" \
% [variable, p_expression]
# ^ use format string to substitute variables in a script
# Should reload the script with changed source code
script.reload()
# Need to create an instance of the script to call its methods
var instance = Reference.new()
instance.set_script(script)
# Evaluate expression here
var result = instance.call("eval")
return result
Another thing you would do it is to write a custom GDScript parser in GDScript to evalulate strings on the fly!
EDIT: flurick’s answers your question by using a specialized Expression class.