eulerangle not work with joystick

hi now i am working on my game the idea about rotate the gun in different ways with move it i had two control options first is accelemerator in the script of accelemerator i wrote this

unction Update () {

transform.eulerAngles.z = 0;

}

that is make gun rotate well without make it looks stupid

but when i try to write it in joystick script it doesn't work

so how to use

unction Update () {

transform.eulerAngles.z = 0;

with joystick ?