C# how to ingore null return

Question

Hi, i'm trying to make a strategy game in the style of warcraft, and i have ran into this problem while programming my basic unit. i have to functions one that returns the nearest (with the maximun range of 30) GameObject that has the Unit script and has a different tag , and the other returns the nearest GameObject that has the one of the following tags "Forest", "Mine", "Farm", "Boulder". the problem is that the script stops because the two functions return null witch is supposed to happen, but i want the script to ignore the 'returned null' error and continue executing. how do i do that ?

edit(moved from comment, reformatted)

 if(AttackTarget!=null)
     Attack(target);
 else if(TargetResource!=null)
     Gather("Farm");

 if(target==null || TargetResource==null)
 {
     if(FindEnemy()!=null)
     {
         target = FindEnemy();
     }
     else if(FindNearestWithTag("Farm")!=null)
     {
         TargetResource = FindNearestWithTag("Farm");
     }
     else
     {
         if(Vector3.Distance(transform.position,myBase.Destination)>5f)
         {
             transform.LookAt(myBase.Destination); velocity = speed; }else{ velocity = 0;} } }

and this is the functions i have for finding enemies and resources:

 Transform FindEnemy()
 {
     Unit[] gos = FindObjectsOfType(typeof(Unit)) as Unit[];
     GameObject closest = null;
     float distance = myBase.teritory;
     Vector3 position = transform.position;
     foreach (Unit go in gos)
     {
         Vector3 diff = go.gameObject.transform.position - position;
         float curDistance = diff.sqrMagnitude;
         if (curDistance < distance && go.gameObject.tag!=this.gameObject.tag)
         {
             closest = go.gameObject;
             distance = curDistance;
         }
     }
     return closest.transform;
 }

 Transform FindNearestWithTag(string target)
 {
     GameObject[] gos = GameObject.FindGameObjectsWithTag(target);
     GameObject closest = null;
     float distance = Mathf.Infinity;
     Vector3 position = transform.position;

     foreach (GameObject go in gos)
     {
         Vector3 diff = go.transform.position - position;
         float curDistance = diff.sqrMagnitude;
         if(go.tag=="Farm")
         {
             if (curDistance < distance&&go.GetComponent<Farm>().isEmpty==false)
             {
                 closest = go;
                 distance = curDistance;
             }  
         }
         else
         {
             if (curDistance < distance)
             {
                 closest = go;
                 distance = curDistance;
             }
         } 
     }
     return closest.transform;
 }

thanks for reading :)

Answer 1

Answer by GibTreaty · May 25, 2012 at 06:59 PM

 GameObject target = GetClosestTarget(30);
     
 if(target != null) {
     //Do stuff
 }

Add comment · Show 2 · Share

user-12161 (google) · May 26, 2012 at 08:44 AM 0

Share

this is what i have in my update.

if(AttackTarget!=null) Attack(target); else if(TargetResource!=null) Gather("Farm");

if(target==null || TargetResource==null){ if(FindEnemy()!=null){ target = FindEnemy(); }else if(FindNearestWithTag("Farm")!=null){ TargetResource = FindNearestWithTag("Farm"); }else{ if(Vector3.Distance(transform.position,myBase.Destination)>5f) { transform.LookAt(myBase.Destination); velocity = speed; }else{ velocity = 0;} } }

and this is the functions i have for finding enemies and resources:

Transform FindEnemy(){ Unit[] gos = FindObjectsOfType(typeof(Unit)) as Unit[]; GameObject closest = null; float distance = myBase.teritory; Vector3 position = transform.position;

     foreach (Unit go in gos) {
         Vector3 diff = go.gameObject.transform.position - position;
         float curDistance = diff.sqr$$anonymous$$agnitude;
         if (curDistance < distance && go.gameObject.tag!=this.gameObject.tag) {
             closest = go.gameObject;
             distance = curDistance;
         }
     }
     return closest.transform;
 }
 
 Transform FindNearestWithTag(string target){
     GameObject[] gos = GameObject.FindGameObjectsWithTag(target);
     GameObject closest = null;
     float distance = $$anonymous$$athf.Infinity;
     Vector3 position = transform.position;
     
     foreach (GameObject go in gos) {
         Vector3 diff = go.transform.position - position;
         float curDistance = diff.sqr$$anonymous$$agnitude;
     if(go.tag=="Farm"){
             if (curDistance < distance&&go.GetComponent<Farm>().isEmpty==false) {
                 closest = go;
                 distance = curDistance;
             }    
     }else {
             if (curDistance < distance) {
                 closest = go;
                 distance = curDistance;
             }
         } 
     }
     return closest.transform;
 }

so yeah that solution doesn't exactly work for me. thanks for replying.

Bunny83 · May 26, 2012 at 10:06 AM 0

Share

What do you mean it doesn't wotk exactly for you? What i can see is that you call your Attach function with the target variable as parameter, but you don't check if target is null. You check ins$$anonymous$$d AttackTarget which isn't even used to call that function...

Answer 2

Answer by Bunny83 · May 26, 2012 at 10:18 AM

You have several things which could break your code:

Your FindEnemy function's last line will produce a null-ref-exception when there is no enemy in range. return closest.transform when closest is null you can't access it's transform...
Same thing for FindNearestWithTag
You call your Attach function without checking the target value for null

Add comment · Share

C# how to ingore null return

2 Replies

Your answer

Follow this Question

Related Questions