Gradle - How to define optional extra property in settings.gradle

Question

I would like to be able to use an optional extra property in my file build.gradle. To do that, I have to check if the property is defined but I have the following error

Cannot get property 'prop' on extra properties extension as it does not exist

File build.gradle

[...]
def my_prop=''
if(gradle.ext.prop!= null && gradle.ext.prop != '')
    my_prop=gradle.ext.prop

It is working with this file setting.gradle

gradle.ext.prop='PROP'

It is not working when I commented line in file setting.gradle

//gradle.ext.prop='PROP'

How can I check in build.gradle that the gradle.ext.prop exists ?

Answer 1

The ext property is of type ExtraPropertiesExtension : see this DSLdocumentation.

To summarize:

• the get(propName) method will throw UnknownPropertyException if the property is not set,
• the has(propName) method can be used to check if a property is set before trying to access it

In your case, you could use has(name) method as follows

def my_prop = ''
if (gradle.ext.has("prop") && gradle.ext.prop != '') {
    println "Property PROP  found: $gradle.ext.prop"
    my_prop = gradle.ext.prop
    // or:  my_prop = gradle.ext('prop')
} else {
    println "Property PROP not set."
}