unity random number from list code example

Example 1: unity random object from list

that's a good question. Randomly pick one item from a list is easy. You can simply do something like :

 myListOfItems[Random.Range(0, myListOfItems.Length)] // if it's an array
 myListOfItems[Random.Range(0, myListOfItems.Count)] // if it's a List
 
But picking a given number of items from a list is a bit more interesting.

Let me give this a try and explain through it. Let's begin with the method signature (our goal).
 
 public static List<T> GetRandomItemsFromList<T> (List<T> list, int number)
 
 
This will be a generic method, with type T so that it can work with a list of anything. It will take a list, and a number of items to pick for parameters. Then, we want to duplicate the input list, so that we can remove items from it as we add them to a new list. Eventually, we want to return the new list.

 // this is the list we're going to remove picked items from
 List<T> tmpList = new List<T>(list);
 // this is the list we're going to move items to
 List<T> newList = new List<T>();
 return newList;
Now we want to loop and move items from one list to the other.

 // make sure tmpList isn't already empty
 while (newList.Count < number && tmpList.Count > 0)
 {
     int index = Random.Range(0, tmpList.Count);
     newList.Add(tmpList[index]);
     tmpList.RemoveAt(index);
 }
So, here's the whole method :

 public static List<T> GetRandomItemsFromList<T> (List<T> list, int number)
 {
     // this is the list we're going to remove picked items from
     List<T> tmpList = new List<T>(list);
     // this is the list we're going to move items to
     List<T> newList = new List<T>();
 
     // make sure tmpList isn't already empty
     while (newList.Count < number && tmpList.Count > 0)
     {
         int index = Random.Range(0, tmpList.Count);
         newList.Add(tmpList[index]);
         tmpList.RemoveAt(index);
     }
 
     return newList;
 }
And this is how to use it :

 List<Item> randomItems = GetRandomItemsFromList<Item> (allItems, 5);

Example 2: unity random object from list

public static List<T> GetRandomItemsFromList<T> (List<T> list, int number)