assigning script to dynamically created button

Question

I have a script main.cs which creates a prefabricated button based on this SO post. I thought btnController.cs was providing the methods for the Button created in main.cs? Why would it have a casting issue?

Error

Assets/scripts/main.cs(21,51): error CS0030: Cannot convert type `UnityEngine.UI.Button' to `btnController'

main.cs

using UnityEngine;
using System.Collections;
using UnityEngine.UI;

public class main : MonoBehaviour {

    public Button myButtonPrefab;

    // Use this for initialization
    void Start () {
        createButton ("minion");
    }

    // Update is called once per frame
    void Update () {

    }

    //this is giving a button prefab all the methods from the class btnController
    void createButton(string name){
        btnController b = ((btnController)Instantiate(myButtonPrefab));
        b.Setup(name,0);
    }
}

btnController.cs

using UnityEngine;
using System.Collections;

public class btnController : MonoBehaviour {
    string name="";
    int value=0;

    public void Setup(string n, int v){
        name = n;
        value = v;
    }

    void OnClick(){
        Debug.Log("btn clicked");
    }
}

Answer 1

Instantiate will always give you an object. The better way to do that is first convert it in GameObject then access your script from there.

GameObject go = Instantiate (myButtonPrefab) as GameObject;
btnController bc = go.GetComponent<btnController>();
bc.Setup(name,0);

It is for when your prefab has already btnController attached.

If you want to add script, do that as,

btnController bc = go.AddComponent<btnController>();
bc.Setup(name,0);