Objective
Main objective of this blog post is to give you a brief idea on how to use WaitUntil & WaitWhile in your project.
Step 1 Concept of WaitUntil & WaitWhile in Unity
Getting confused with WaitUntil & WaitWhile?
Don’t know how to use WaitUntil & WaitWhile?
If that’s the case, then I’m at your service.
I assume you already know about coroutines before reading this blog post, as WaitUntil and WaitWhile works only with a yield statement in coroutines.
If not, then have a look here:
Step 2 Understand about WaitUntil
- By definition, it holds back the execution until the condition gets true.
- In other words, it will not continue the execution when our condition has a false value. Unity will wait for the condition to get a true value to continue execution.
Okay, I got the Idea. What next?
Now we’ll move on to a simple demo so that you know how and where to use it.
Say you are developing a car racing game and you want to give a notification to player as soon as the tank gets empty.
For that case, check out following code:
using UnityEngine;
using System.Collections;
public class Demo : MonoBehaviour {
public int counter;
void Start() {
counter = 20;
StartCoroutine(FuelNotification());
}
IEnumerator FuelNotification() {
Debug.Log("Waiting for tank to get empty");
yield return new WaitUntil(()=> counter <= 0);
Debug.Log("Tank Empty!"); //Notification
}
void Update() {
if (counter > 0)
{
Debug.Log("Fuel Level: " + counter);
counter--;
}
}
}
When counter becomes zero, player will get the notification. And until then console will display fuel level.
Pretty simple, isn’t it?
Yeah! But what is this mysterious “() =>” thing with our WaitUntil?
Well, I was expecting that question from you.
That thing is called A Lambda expression. (Only => part, not the parentheses)
It is an Anonymous method (another C# concept) which implicitly gets the info about the variable passed with it. It is mostly used in LINQ expressions.
Lambda expression is a very convenient tool, give it a try. See how that works here:
However, if that messes up your head, we’ve another way for doing things:
using UnityEngine;
using System.Collections;
public class Demo : MonoBehaviour {
public int counter;
void Start() {
counter = 20;
StartCoroutine(FuelNotification());
}
IEnumerator FuelNotification() {
Debug.Log("Waiting for tank to get empty");
yield return new WaitUntil(IsTankEmpty);
Debug.Log("Tank Empty!");
}
void Update() {
if (counter > 0)
{
Debug.Log("Fuel Level: " + counter);
counter--;
}
}
public bool IsTankEmpty(){
if(counter>0){ return false; }
else { return true; }
}
}
Check console; output is the same, right?
Got the point? A whole method in just one line, see how powerful a Lambda Expression is.
I hope that cleared your thoughts on WaitUntil.
Step 3 Understand about WaitWhile
- WaitWhile is the opposite of WaitUntil.
- It holds back the execution while the condition is true.
- Unlike WaitUntil, it will wait for the condition to get a false value to execute next code block.
The same example as before using WaitWhile would be as following:
using UnityEngine;
using System.Collections;
public class Demo : MonoBehaviour {
public int counter;
void Start() {
counter = 20;
StartCoroutine(FuelNotification());
}
IEnumerator FuelNotification() {
Debug.Log("Waiting for tank to get empty");
yield return new WaitWhile(()=> counter > 0);
Debug.Log("Tank Empty!");
}
void Update() {
if (counter > 0)
{
Debug.Log("Fuel Level: " + counter);
counter--;
}
}
}
As you can see, only the mechanism of dealing with conditions is different. Rest is the same.
Step 4 Conclusion
But keep in mind that using these concepts is like a double edged sword.
If your calculations are huge, this will slow down your game’s performance as these functions are called in each frame.
With this, I would like to end this post on WaitUntil & WaitWhile.
If you still find anything in this post confusing, drop a comment below.
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An Addictive Gamer turned into a Professional Game Developer. I work with Unity Engine. Part of TheAppGuruz Team. Ready to take on Challenging Games & increase my knowledge about Game Development.