how to call a function from node block scripted pipeline - jenkins-pipeline

Question

am trying to understand the below line why do we need to call a stage with .call()
buildStage(slurper).call() can someone explain me what this line means why cant we just call with
buildStage(slurper)
def call(String jsonString) {
node("unix") {
try {
def slurper = new JsonSlurperClassic().parseText(jsonString)
buildStage(slurper).call()
deployStage()
}catch(error) {
println ex.toString()
}finally{
sendEmail()
}
}
}
def buildStage(slurper){
stage ('Build') {
}
}
def deployStage(slurper){
stage ('Deploy') {
}
}

Answer 1

From your above example buildStage(slurper).call() is not needed as it can be called like buildStage(slurper),
methondName.call() is needed if the method has a closure block that needs to be executed upon calling, see my below example
myPipeline.groovy
import groovy.json.JsonSlurperClassic
def call(String jsonString) {
node() {
try {
def slurper = new JsonSlurperClassic().parseText(jsonString)
buildStage(slurper)
println deployStage(slurper).call()
}catch(Exception ex ) {
throw ex;
}finally{
// do nothing
}
}
}
def buildStage(slurper){
stage ('Build') {
return {
println slurper
def r = 5 + 5
println r
}.call()
}
}
def deployStage(slurper){
stage ('Deploy') {
return {
return "The name is "+ slurper.name
}
}
}
Jenkinsfile
def myJSON = '''
{ "name" : "XYZ"}
'''
myPipeline(myJSON)