rosserial working, arduino not outputing

edit

First off, I am Publishing String Data on a "set_pins_mode" topic. When I echo the topic, the data looks like this

---
Data: lights on

When I set up the arduino, everything seems to connect good but I am not getting an output. I believe it may be in the data structure or something. Here is my simplified arduino code.

#include <ros.h>
#include <std_msgs/String.h>

ros::NodeHandle  nh;

String Pin;

int Lights = 22;

void messageCb( const std_msgs::String& str_msg){

  Pin = str_msg.data;

}

ros::Subscriber(std_msgs::String)  sub("set_pins_mode", &messageCb);

void setup(){ 

  pinMode(13, OUTPUT);

  nh.initNode();

  nh.subscribe(sub);

  //Set all the pins we need to output pins

  pinMode(Lights, OUTPUT);

}

void loop()
{  

  if (Pin = "light on"){

    digitalWrite(Lights, HIGH);
  }

  if (Pin = "light off"){

    digitalWrite(Lights, LOW);
  }


nh.spinOnce();

delay(1);
}

The program will get more complex with more lights added. I wanted to try and get one light working first, then its just a simple thing of copy/paste. I know this has to be easy. The output just doesn't come on.