unity cannot implicitly convert type float' to bool' also Make the camera zoom?

Question

I use C# and I'm new. I am trying to make a zoom function for a game on unity. Here is my code (that I have so far):

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Zoom : MonoBehaviour
{
    public Camera cam;
    public float zoom_speed = 20f;

    // Update is called once per frame
    void Update ()
    {
        if(Input.GetAxis("Mouse ScrollWheel"))
        {
            cam.fieldOfView = zoom_speed;
        }
    }
}

However, I am getting the error "cannot implicitly convert type float to bool when I hover over if(Input.GetAxis("Mouse Scrollwheel")) Also any advice on how to make the zoom program work would be much appreciated.

Answer 1

The Input.GetAxis("Mouse ScrollWheel"); script return a float value.

The value will be in the range -1...1 for keyboard and joystick input. If the axis is setup to be delta mouse movement, the mouse delta is multiplied by the axis sensitivity and the range is not -1...1.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Zoom : MonoBehaviour
{
    public Camera cam;
    public float zoom_speed = 20f;

    // Update is called once per frame
    void Update ()
    {
         float d = Input.GetAxis("Mouse ScrollWheel");
         if (d > 0f)
         {
            //Positive value
            //Scroll up
            cam.fieldOfView += zoom_speed;
         }
         else if (d < 0f)
         {
            //Negative value
            //Scroll down
            cam.fieldOfView -= zoom_speed;
         }

    }
}