gradle/groovy : calling a 'global' function from a custom Class

Question

I'm new to groovy/gradle As far as I understand gradle/groovy is compatible with java.

I wrote the following gradle (without any task) in a 'build.gradle' file:

def myFun = {->"Hello World"}

class MyClass {
    String getLabel() {
        return ""+ myFun();
        }
    }

System.err.println(new MyClass().getLabel());

where a class MyClass calls the 'global'(?) function myFun.

Calling gradle --tasks produces the following error:

FAILURE: Build failed with an exception.

* Where:
Build file 'build.gradle' line: 6

* What went wrong:
A problem occurred evaluating root project 'tmp'.
> No signature of method: MyClass.myFun() is applicable for argument types: () values: []
  Possible solutions: find(), find(groovy.lang.Closure), wait(), any(), every(), dump()

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

BUILD FAILED

Total time: 2.671 secs

How can I make this class MyClass to 'see' the function myFun ?

Thank you.

I believe you meant `gradle tasks` and not `gradle --tasks`. — nickb, Nov 29 '18 at 15:15

score 2 · Accepted Answer · answered Nov 29 '18 at 15:14

You can't directly, since there are no global variables in Groovy. You can modify your declaration to pass an instance of the current class so you can invoke the myFun closure:

@groovy.transform.Field 
def myFun = {-> "Hello World"}

class MyClass {
    String getLabel(script) {
        return ""+ script.myFun();
    }
}

System.err.println(new MyClass().getLabel(this))

Or you can use the binding object, but it's the same pattern.

For more info:

gradle/groovy : calling a 'global' function from a custom Class

1 Answers1