[FIXED] How do I reassign parameters in a Jenkins pipeline script?

Issue

I'm new to Jenkins and groovy scripting. I'm trying to reassign the parameters in the Jenkins script.

I tried the following

def reasignParams() {
    if(params.B == '') {
       params.B = params.A
    }
}

pipeline{
    parameters {
         string(name: 'A', defaultValue: '1.1', description: "Master Value")
         string(name: 'B', defaultValue: '', description: "Slave value")
    }
}

After running the above Jenkins pipeline script (groovy), I ran into the following error

java.lang.UnsupportedOperationException

The alternative that I thought to this is as below

def reasignParams() {
        if(params.B == '') {
           def temp = params.A
           # use temp variable instead of params.B; But this is inconvenient
        }
    }

I would like to learn if there is a way to reassign parameters in the Jenkins pipeline script? Any help would be greatly appreciated, Thanks in advance!

Solution

The params object in Jenkins Pipeline does not support write operations on its member variables. You can only initially assign them in the parameters directive (think of it like a constructor in that sense). If you want to reassign parameter values, then you do indeed need to make a deep copy like the following:

newParams = [:]
newParams.A = params.A

Answered By - Matt Schuchard