Scope of the extra properties in Gradle? - properties

Question

I have a Gradle script similar to this:
ext {
dir = null
}
task init << {
build()
}
task buildAll(type: Exec){
workingDir ext.dir
commandLine 'cmd', '/c', "echo %JAVA_HOME%"
}
def build(){
ext.dir = "asdf"
buildAll.execute()
}
When I run the script, I get:
groovy.lang.MissingPropertyException: Cannot get property 'dir' on extra properties extension as it does not exist
Whatever I tried, I couldn't get a task to read a property from "ext". It can be seen from methods (like "build()" in my example), but not from any other task except the default one ("init" in my example).
I understand that the "ext" properties should be accessible from anywhere inside the project, so what am I doing wrong?
UPDATE:
The workflow I'm trying to achieve (as asked by Opal):
I have several environments I need to build with one script. Each of these environments is listed in a CSV file with a line: <environment>,<version>.
Script then needs to do the following:
Delete existing directory
Checkout code from SVN into new directory (both directory and SVN url depend on environment and version)
Copy some settings files (paths depend on version)
Edit some of those settings files (values depend on environment and version)
Set some environment variables (JAVA_HOME, ANT_HOME...) (depends on version)
Run three build commands (${ANT_HOME}/bin/ant -f $checkedOutCodeDirectory/Build/build-all.xml target1, then target2 and target3)
This needs to be executed for each environment

Answer 1

Extra properties should be created via ext but referred via project instance without any instance at all so: project.dir or dir, so the first change to script will be:
ext {
dir = null
}
task init << {
build()
}
task buildAll(type: Exec){
workingDir dir // ext.dir -> dir
commandLine 'cmd', '/c', "echo %JAVA_HOME%"
}
def build(){
ext.dir = "asdf"
buildAll.execute()
}
Now, before any task or method is executed the script is read and parsed, sot the whole body of buildAll will be configured before any other part is run. Thus it will always fail, since dir property has no value. Proof:
ext {
dir = null
}
task init << {
build()
}
task buildAll(type: Exec){
workingDir dir ? dir : project.rootDir
commandLine 'cmd', '/c', "echo %JAVA_HOME%"
}
def build(){
ext.dir = "asdf"
buildAll.execute()
}