Capturing results of Jenkins input step - jenkins

Question

I am playing around with the Jenkins Pipeline and I have some issues at the time of capturing the results of an input step. When I declare the input step as follows ...
stage('approval'){
steps{
input(id: 'Proceed1', message: 'Was this successful?',
parameters: [[$class: 'BooleanParameterDefinition', defaultValue: true, description: '', name: 'Please confirm you agree with this']])
}
}
... everything seems to be working fine. However, as soon as I try to get the results from the capture (i.e. the answer given to the question), the script does not work. For example, an script like the following:
pipeline {
agent { label 'master' }
stages {
stage('approval'){
steps{
def result=input(id: 'Proceed1', message: 'Was this successful?', parameters: [[$class: 'BooleanParameterDefinition', defaultValue: true, description: '', name: 'Please confirm you agree with this']])
echo 'echo Se ha obtenido aprobacion! (como usar los datos capturados?)'
}
}
}
}
... results in the following error:
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
WorkflowScript: 6: Expected a step # line 6, column 13.
result=input(id: 'Proceed1', message: 'Was this successful?', parameters: [[$class: 'BooleanParameterDefinition', defaultValue: true, description: '', name: 'Please confirm you agree with this']])
^
1 error
at org.codehaus.groovy.control.ErrorCollector.failIfErrors(ErrorCollector.java:310)
at org.codehaus.groovy.control.CompilationUnit.applyToPrimaryClassNodes(CompilationUnit.java:1073)
at org.codehaus.groovy.control.CompilationUnit.doPhaseOperation(CompilationUnit.java:591)
at org.codehaus.groovy.control.CompilationUnit.processPhaseOperations(CompilationUnit.java:569)
...
at hudson.model.Executor.run(Executor.java:404)
Finished: FAILURE
Something quite interesting is that if I moved the input outside the pipeline{}, it works perfectly fine. I noticed that same behaviour occurs with 'def' statement (I can define and use a variable outside pipeline{} but I cannot define it inside).
I think I must be missing something quite basic here but after few hours trying different configurations, I could not manage to make it work. Is it just that the logic to be used within pipeline{} is limited to very few commands? How people then build complex pipelines?
Any help would be highly appreciated.

Answer 1

The script block allows using the Scripted Pipeline syntax aka almost all Groovy functionality within a Declarative pipeline.
See https://jenkins.io/doc/book/pipeline/syntax/ for syntax comparision and restrictions of the declarative pipeline.
pipeline {
agent any
...
stages {
stage("Stage with input") {
steps {
script {
def result = input(id: 'Proceed1', message: 'Was this successful?', parameters: [[$class: 'BooleanParameterDefinition', defaultValue: true, description: '', name: 'Please confirm you agree with this']])
echo 'result: ' + result
}
}
}
}
}

Answer 2

I finally managed to make it work but I had to completely change the syntax to avoid pipeline, stages & steps tags as used above. Instead, I implemented something like:
#!/usr/bin/env groovy
node('master'){
// --------------------------------------------
// Approval
// -------------------------------------------
stage 'Approval'
def result=input(id: 'Proceed1', message: 'Was this successful?', parameters: [[$class: 'BooleanParameterDefinition', defaultValue: true, description: '', name: 'Please confirm you agree with this']])
echo 'Se ha obtenido aprobacion! '+result
}