Unity 4.6无法将类型'UnityEngine.Component'隐式转换为'DamageInterface'

Question

I am having an issue trying to get my game to compile, the issue stems from my damage interface script and my projectile script. The error code in the console is as follows.

Assets/Scripts/Projectile.cs(32,33): error CS0266: Cannot implicitly convert type UnityEngine.Component' to DamageInterface'. An explicit conversion exists (are you missing a cast?)

DamageInterface.cs

using UnityEngine;
using System.Collections;
//damage interface

public interface DamageInterface {

    void TakeHit (float damage, RaycastHit hit);

}

Projectile.cs

using UnityEngine;
using System.Collections;

public class Projectile : MonoBehaviour {

    public LayerMask collisionMask; //detect what layer projectile collides with 
    float speed = 10;
    float damage = 1;

    public void SetSpeed(float newSpeed) {
        speed = newSpeed;
    }

    void Update () {
        float moveDistance = speed * Time.deltaTime;
        CheckCollisions (moveDistance);
        transform.Translate (Vector3.forward * moveDistance);
    }


    void CheckCollisions(float moveDistance) { //raycast to detect collision
        Ray ray = new Ray (transform.position, transform.forward);
        RaycastHit hit;

        if (Physics.Raycast(ray, out hit, moveDistance, collisionMask)) {
            OnHitObject(hit);
        }
    }


    void OnHitObject(RaycastHit hit) {
        DamageInterface damageableObject = hit.collider.GetComponent(typeof(DamageInterface)); //ERROR RESIDES HERE
        if (damageableObject != null) {
            damageableObject.TakeHit(damage, hit); //damage + raycast hit
        }
        GameObject.Destroy (gameObject); //destroy projectile if enemy layer is hit
    } 
}

I believe I have used the typeof(T) approach to get my interface component but I must be missing something clearly. Thanks

The error resides on this line in my Projectile.cs:

DamageInterface damageableObject = hit.collider.GetComponent(typeof(DamageInterface));

Answer 1

In Unity5.x you can fetch component that are interfaces like this:

IInterface myInterface = gameObject.GetComponent<IInterface>();

in older version you need to perform a cast:

 IInterface myInterface = (IInterface)gameObject.GetComponent(typeof(IInterface));

this is because GetComponent returns a Component and your interface is not. The error actually tells you what to do:

An explicit conversion exists (are you missing a cast?)

Yes you were missing the cast.