How do I create and access the global variables in Groovy?

Question

I need to store a value in a variable in one method and then I need to use that value from that variable in another method or closure. How can I share this value?

score 258 · Answer 1 · edited Mar 04 '21 at 13:09

258

In a Groovy script the scoping can be different than expected. That is because a Groovy script in itself is a class with a method that will run the code, but that is all done runtime. We can define a variable to be scoped to the script by either omitting the type definition or in Groovy 1.8 we can add the @Field annotation.

import groovy.transform.Field

var1 = 'var1'
@Field String var2 = 'var2'
def var3 = 'var3'

void printVars() {
    println var1
    println var2
    println var3 // This won't work, because not in script scope.
}

edited Mar 04 '21 at 13:09

Neuron

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answered Jun 11 '11 at 11:27

mrhaki

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38

Just to note Field @requires an import.. import groovy.transform.Field – khylo Jan 09 '13 at 10:43
funny tried to edit to change then to than in the first line, SO wants a six-char edit! – JimLohse Jan 15 '16 at 18:50
1

if you're trying to use a global variable from within a class definition, it gets a bit tricky. The `class Globals` solution below is a way around that. – solstice333 Apr 03 '17 at 21:50
8

I tried the `var1 = 'var1'` method in a Jenkins Pipeline using Groovy and it didn't work. I had to use `@Field var1 = 'var1'` – retsigam Aug 02 '18 at 16:55

score 67 · Answer 2 · edited Mar 04 '21 at 13:08

def i_am_not_global = 100 // This will not be accessible inside the function

i_am_global = 200 // this is global and will be even available inside the 

def func()
{
    log.info "My value is 200. Here you see " + i_am_global
    i_am_global = 400
    //log.info "if you uncomment me you will get error. Since i_am_not_global cant be printed here " + i_am_not_global 
}
def func2()
{
   log.info "My value was changed inside func to 400 . Here it is = " + i_am_global
}
func()
func2()

here i_am_global variable is a global variable used by func and then again available to func2

if you declare variable with def it will be local, if you don't use def its global

score 62 · Answer 3 · edited Jun 10 '11 at 17:01

62

class Globals {
   static String ouch = "I'm global.."
}

println Globals.ouch

edited Jun 10 '11 at 17:01

Dónal

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answered Jun 10 '11 at 11:53

Bob Herrmann

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score 5 · Answer 4 · answered Jun 10 '11 at 11:50

Like all OO languages, Groovy has no concept of "global" by itself (unlike, say, BASIC, Python or Perl).

If you have several methods that need to share the same variable, use a field:

class Foo {
    def a;

    def foo() {
        a = 1;
    }
    def bar() {
        print a;
    }
}

score 1 · Answer 5 · edited Jul 04 '13 at 21:27

1

I think you are talking about class level variables. As mentioned above using global variable/class level variables are not a good practice.

If you really want to use it. and if you are sure that there will not be impact...

Declare any variable out side the method. at the class level with out the variable type

eg:

{
   method()
   {
      a=10
      print(a)
   }

// def a or int a wont work

a=0

}

edited Jul 04 '13 at 21:27

GrandMasterFlush

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answered Jul 04 '13 at 20:59

Pruthvi Minchinadka

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It may not be a clean approach, but it works ;) thanks. – Nicole Stutz Aug 03 '16 at 11:42

score 1 · Answer 6 · answered Dec 30 '14 at 23:57

def sum = 0

// This method stores a value in a global variable.
def add =
{ 
    input1 , input2 ->
    sum = input1 + input2;
}

// This method uses stored value.
def multiplySum =   
{
    input1 ->
        return sum*input1;
}

add(1,2);
multiplySum(10);

score 1 · Answer 7 · answered Jun 10 '11 at 11:50

1

Just declare the variable at class or script scope, then access it from inside your methods or closures. Without an example, it's hard to be more specific for your particular problem though.

However, global variables are generally considered bad form.

Why not return the variable from one function, then pass it into the next?

answered Jun 10 '11 at 11:50

tim_yates

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1

what if i want to use the variable whose value have been assigned within a closure? E.g: i have def a = null at the beginning of the script. Now the inside a closure, the value of a = 'some string' , is assigned. I want this new value to be accessible to all other closures. thanks – OK999 Oct 26 '17 at 18:30
Really? You'll hate yourself when you have to try and fix it – tim_yates Oct 27 '17 at 06:20
I ended creating a closure that returns the desired calculated value and using that where its needed – OK999 Oct 27 '17 at 13:24

score 0 · Answer 8 · answered Jun 11 '11 at 07:23

Could not figure out what you want, but you need something like this ? :

def a = { b -> b = 1 }
bValue = a()
println b // prints 1

Now bValue contains the value of b which is a variable in the closure a. Now you can do anything with bValue Let me know if i have misunderstood your question

How do I create and access the global variables in Groovy?

8 Answers8

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