groovy evaluate string as the function which exists in the same script - groovy

Question

I am trying to evaluate string as code in groovy and it is failing with groovy.lang.MissingMethodException exception even though method exists in the same script. As I understood groovy runs new instance every time it tries to evaluate the code, but is there any way to inject current script into Eval.me or GroovyShell().evaluate() so that it can find the method and runs it ?
Below is sample code snippet,
def justSayHello(){
return "hello"
}
def my_str = "justSayHello()"
//Eval.me(my_func_str)
new GroovyShell().evaluate(my_func_str)
Both Eval and GroovyShell().evaluate() are throwing below exception
Caught: groovy.lang.MissingMethodException: No signature of method: Script1.justSayHello() is applicable for argument types: () values: []
groovy.lang.MissingMethodException: No signature of method: Script1.justSayHello() is applicable for argument types: () values: []
at Script1.run(Script1.groovy:1)
at string_split.run(string_split.groovy:35)

Answer 1

The following code:
justSayHello = {
println "hello"
}
def my_str = "justSayHello()"
new GroovyShell(binding).evaluate(my_str)
prints out hello when run. Here we have changed justSayHello from a method (on an implicit class that you can not see but which the groovy compiler generates around your script) to a closure. Further we are not doing def justSayHello as that would be defining it as a field on the implicit surrounding class (again which you can't see, but it's there), but rather just defining the variable without any modifiers which puts it in the global binding of the script.
We then send in the binding to the GroovyShell so that it can find the variable.
Result:
─➤ groovy solution.groovy
hello
A more generic variant is to do something like this:
def justSayHello() {
println "hello"
}
def someOtherMethod() {
println "hello again"
}
def methods = this.class.declaredMethods.findResults { m ->
if (m.name.startsWith('$') || m.name in ['main', 'run']) return null
[m.name, this.&"${m.name}"]
}.collectEntries { it }
// just for debugging, print the methods
methods.each { k, v ->
println "method: $k"
}
def my_str = "justSayHello()"
new GroovyShell(new Binding(methods)).evaluate(my_str)
which prints:
─➤ groovy solution.groovy
method: justSayHello
method: someOtherMethod
hello
here we find all the declared methods in the implicit class generated by groovy, remove some stuff added by the groovy compiler (namely main, run and methods starting with a $) and then send the resulting map as the binding for the GroovyShell constructor.
I suspect there might be a more elegant way of accomplishing this, so any groovy gurus - feel free to correct me here.
For an explanation of the implicit enclosing class for a groovy script, see for example this stackoverflow answer.