Check if Binding Variable is defined

In scripting, its helpful to create global variables. It’s definitely not a good idea for any form of scalability, obviously, but Groovy has done a good job in creating this slight separation of function.

myBindingVar = 'checkme' //binding occurs, so that it is available everywhere
def myLocalVar = 'not useful' //this is a local variable that is only available to the local scope
String myLocalString = 'also not useful' //this is also a local variable that is only available to the local scope

The difference is that the following won’t work:

def myLocalVar = 'not useful' //this is a local variable that is only available to the local scope
def myFunc() {
    println myLocalVar //this will throw an error, because it is out of scope
}
myFunc()

but the following will work:

myBindingVar = 'checkme' //binding occurs, so that it is available everywhere
def myFunc() {
    println myBindingVar
}
myFunc()

This can cause some problems in scripting if you need to either provide default values or if you need it to provide a better exception if the variable isn’t found.

An easy solution to this is the following:

if (binding.variables.containsKey("bindingVar")) {
    // do something
}

Or if you’d like to get a null value for an optional binding:

def optVar = binding.variables.get("bindingVar")
if (optVar) {
    // do something
}

Similarly, when using Gradle, which is based off of Groovy, you can define one or more gradle.properties files. An example gradle properties would be as simple as:

myProp=checkMe

use the following to determine if a property is defined:

if (gradleProject.properties.containsKey("myProp")) {
    // do something
}

Or if you’d like to get a null value for an optional property:

if (gradleProject.properties['myProp']) {
    // do something
}