MonoBehaviour.Invoke
Thank you for helping us improve the quality of Unity Documentation. Although we cannot accept all submissions, we do read each suggested change from our users and will make updates where applicable.
Submission failed
For some reason your suggested change could not be submitted. Please <a>try again</a> in a few minutes. And thank you for taking the time to help us improve the quality of Unity Documentation.
Declaration
Description
Invokes the method methodName in time seconds.
If time is set to 0 and Invoke is called before the first frame update, the method is invoked at the next Update cycle before MonoBehaviour.Update. In this case, it’s better to call the function directly.
Note: Setting time to negative values is identical to setting it to 0.
In other cases, the order of execution of the method depends on the timing of the invocation.
If you need to pass parameters to your method, consider using Coroutine instead. Coroutines also provide better performance.
Invoke unity что это
What if you need to invoke a specific code in 2 seconds? You can write an accumulator that counts time, use coroutine to wait for 2 seconds or simply use Invoke or InvokeRepeating methods.
Invoke
Invoke is a public method of MonoBehaviour class (so you can access it from your game scripts). It takes method name and time as parameters and it can be used in that way:
This example executes LaunchProjectile method 2 seconds after starting. It’s just that simple.
InvokeRepeating
InvokeRepeating is very similar to Invoke method but it takes repeat interval as a third parameter, so there can be a difference between the first execution time and any other. Here’s an example:
In this example LaunchProjectile method will be invoked 2 seconds after starting and then in 0.3 second intervals.
CancelInvoke
CancelInvoke allows you to cancel any pending invoke scheduled using two previous methods. It takes a scheduled method name as a parameter.
You may also want to check if the method is scheduled for invocation using IsInvoking method.
Possible alternatives
Invoke methods may be a nice shortcut when you want to quickly schedule a method to be invoked in the future, but it can be difficult to maintain because of passing a string as a method name. Because of that, the refactoring errors will be visible only in the run time and this usually means trouble.
Instead of using Invoke methods you may prefer to use coroutines. Coroutines are lengthy by nature, but a lot safer to maintain (of course if you’re using StartCoroutine overload that takes IEnumerator value type as parameter instead of string).
Mastering the Invoke Function in Unity: A Comprehensive Guide
Learn how to use the Invoke function in Unity with this step-by-step guide. Understand its importance and discover common issues and their solutions.
If you’re a game developer using Unity, you might have heard about the Invoke function. It allows you to schedule method calls at a later time, which can help you optimize your game and improve its performance. However, if you’re not familiar with how to use invoke in unity , don’t worry — this article is here to help.
What is Invoke in Unity?
Invoke is a function in Unity that enables you to schedule method calls to occur at a later time. This can be helpful if you want to execute a method after a certain amount of time has elapsed or if you want to delay a method call until a specific event occurs.
To use Invoke in Unity, you need to specify the name of the method you want to call, the amount of time to wait before calling the method, and any parameters required by the method. Once you’ve specified these details, Unity will automatically call the method at the scheduled time.
Examples of when Invoke can be used in Unity include delaying an explosion animation until the player has moved out of the way, scheduling a power-up to appear after a set amount of time, or creating a delay between enemy spawns.
How to use Invoke in Unity?
Using Invoke in Unity is a straightforward process. Here’s a step-by-step guide to help you get started:
Step 1: Define the Method to Call
The first step in using Invoke is to define the method you want to call. This could be any method within your script, including Start, Update, or any custom method you’ve created.
Step 2: Specify the Time Delay
Next, you need to specify the amount of time to wait before calling the method. This can be done using a float value, which represents the number of seconds to wait before calling the method.
Step 3: Add any Parameters
If your method requires any parameters, you can specify them after the time delay. Parameters can be of any data type, including integers, floats, or strings.
Step 4: Call the Invoke Method
Once you’ve specified the method, time delay, and any parameters required, you can call the Invoke method. This will schedule the method call to occur at the specified time.
Here’s an example of how to use Invoke in Unity:
In this example, the SpawnEnemy method will be called 5 seconds after the Start method has been called.
Best practices for using Invoke in Unity
Here are some best practices to keep in mind when using Invoke in Unity:
- Use Invoke only when necessary. If you need to schedule a method call that occurs every frame, consider using a Coroutine instead.
- Avoid calling Invoke multiple times in a single frame. This can cause performance issues and slow down your game.
- Be mindful of the time delay you specify. If the delay is too long, it can cause the game to feel unresponsive.
- Use descriptive method names to make it clear what the method does.
C# Invoke in Unity! — Beginner Scripting Tutorial
Alternative to Invoke: Coroutines
While Invoke is a useful function in Unity, it’s not always the best option. In some cases, using Coroutines can be a better choice.
Coroutines are similar to Invoke, but they provide more control over the timing of method calls. With Coroutines, you can specify when a method should be called, how long it should run, and how often it should be called.
Coroutines can be used to optimize your game and improve its performance. For example, you might use a Coroutine to gradually increase the difficulty of your game over time, or to create a smooth camera movement.
Common issues faced while using Invoke and their solutions
While Invoke can be a helpful function in Unity, there are some common issues you might encounter. Here are a few of the most common issues and their solutions:
Issue 1: Delay not working as expected
If the delay you’ve specified for Invoke isn’t working as expected, it might be because you’re calling the function multiple times in a single frame. To fix this, you can use a Coroutine instead.
Issue 2: Method with parameters not working
If you’re trying to use Invoke with a method that requires parameters, you’ll need to use a lambda expression to pass the parameters. Here’s an example:
In this example, the SpawnEnemyWithParams method calls Invoke with a lambda expression that passes the enemyType parameter to the SpawnEnemy method.
Advancements in Invoke functionality in Unity
Unity is constantly improving its functionality, and Invoke is no exception. In recent versions of Unity, new features have been added to Invoke to make it even more powerful.
One of the new features is the ability to cancel an Invoke call. This can be helpful if you need to stop a method from being called after it’s been scheduled.
Another new feature is the ability to call a method repeatedly using InvokeRepeating. This can be useful if you need to execute a method at regular intervals, such as updating the player’s health bar.
Other simple Invoke code samples
In Csharp , for instance, unity invoke code example
Conclusion
In conclusion, understanding how to use the Invoke function in Unity can help you optimize your game and improve its performance. By following the steps outlined in this article, you’ll be able to use Invoke effectively and avoid common issues.
Remember, if you’re struggling with Invoke, you can always use Coroutines as an alternative. And don’t forget to check out the latest advancements in Invoke functionality in Unity to see what new features are available. Happy coding!
How to DELAY a FUNCTION using INVOKE method
This article belongs to an old series of the channel, currently there is a video available that explains better how to use the Invoke function to make a function be called with delay, you can watch it here:
�� How to DELAY a FUNCTION using INVOKE method
Old Article below
Introduction
In this article we are going to see how to use the Invoke method of Unity’s MonoBehaviour class to execute an action with a certain delay. This allows us for example to create mechanisms that work for a while.
Go to the project’s main page
Before we start I invite you to watch the video I made to summarize this article. English Subtitles available.
Procedure
To analyse the Invoke method we’ll be using the GameDevLab’s “Invoke a Method” station, which is a vending machine for the refreshing new GameDevCola that not only quenches thirst but also heals your wounds.
Fig. 1: GameDevLab “Invoke a Method” station. GameDevCola vending machine.
By approaching the machine we can interact with it using the E key. When you press it, the machine will become inactive, that is, you will not be able to interact with it for a while. After a few seconds the machine will eject a can of GameDevCola and seconds later will again be enabled for interaction.
Fig. 2: Script InvokeAMétodo sin completar.
In the script to complete we have the methods “DeliverACola” and “PrepareMachine” that will deliver the drink and enable the machine respectively.
Then we have redefined the OnTriggerStay method that allows us to check if the character is standing in front of the machine.
Within this method we check if the Tag of the GameObject is that of the player, then if the machine is ready (boolean machineReady), we tell the UIManager object that can interact and this is responsible for displaying the message on screen.
Then we check if the E key is pressed. At this point the machine receives a request for a GameDevCola. The first thing you do is deactivate the machine and then in the region with comments is where we must complete the missing code.
Analysis of events in time
I want to emphasize this part because it is important to understand the idea.
When we call a method in C#, the execution of it is done at that precise instant, all instructions are solved even before refreshing the screen image.
So if we called the methods directly in the region marked with comments, what would happen is that the can would be expelled and the machine enabled again in the same instant in which the E key is pressed. As illustrated in the timeline in figure 3.
Fig. 3: Diagram of events in time. This would happen if we called the methods directly.
Figure 3 shows a timeline in which there are two different points in time, the first point being the beginning of the game. Sometime later in time is the second point, in which the player asks for a can, the machine delivers it and it is enabled again, these three actions at the same time.
Fig. 4: Diagram of events in time. This is what we want to achieve.
Figure 4 shows four different time points.
Point 1: Start of the game.
Point 2: The player orders the GameDevCola.
Point 3: X milliseconds after the order is placed, the machine delivers the can.
Point 4: After Y milliseconds of can delivery, the machine is enabled again.
This is what we are going to do using the Invoke method of the MonoBehaviour class.
Solution
The Invoke method can be called directly without reference to a class.
We must indicate two parameters, the first is a String with the name of the method we want to invoke, the second parameter is a float to indicate the number of seconds that will pass until the method is finally executed.
Upper and lower case must be respected. If we get confused at this point, a bug may arise that is difficult to track. If the method is called “DeliverACola” and we invoke the “DeliveraCola” method what will happen is that we will try to call that method but as it is not defined, the program will go ahead without executing those instructions.
Fig. 5: InvokeAMethod script completed.
Figure 5 shows the resolution for the exercise. The can will be delivered two seconds after the player presses the E key and the machine is re-enabled four seconds later.
Fig. 6: When approaching the machine, a sign appears indicating that it is possible to interact.
Fig. 7: After a few seconds of interacting with the machine, we are given a can.
Conclusion
The Invoke method is used to postpone the execution of a method. Although it is not the only way to achieve this, it is a simple resource, easy to remember and easy to implement.
MonoBehaviour.Invoke
Thank you for helping us improve the quality of Unity Documentation. Although we cannot accept all submissions, we do read each suggested change from our users and will make updates where applicable.
Submission failed
For some reason your suggested change could not be submitted. Please <a>try again</a> in a few minutes. And thank you for taking the time to help us improve the quality of Unity Documentation.
Declaration
Description
Invokes the method methodName in time seconds.
If time is set to 0 and Invoke is called before the first frame update, the method is invoked at the next Update cycle before MonoBehaviour.Update. In this case, it’s better to call the function directly.
Note: Setting time to negative values is identical to setting it to 0.
In other cases, the order of execution of the method depends on the timing of the invocation.
If you need to pass parameters to your method, consider using Coroutine instead. Coroutines also provide better performance.
Unity MonoBehaviour.Invoke with C# examples
Hello programmers, In this article, you will learn about Unity MonoBehaviour.Invoke with C# examples.
Before we get started with the building process, we need to know a few concepts. Let’s first discuss them one by one.
MonoBehaviour.Invoke
The Invoke functions enable you to call a function after some specified time delay.
This allows us to build a helpful system to call methods, that is time sensitive.
Syntax:
public void Invoke(string methodName, float time);
Example:
- Attach the InvokeScript to the GameObject obstacle.
- In the Invoke Script, we can see a public GameObject named obstacle.
- We also have a method named SpawnObstacle.
- The SpawnObstacle method will simply Instantiate the obstacle object.
- As we can see in the start method, we call the Invoke function.
- Invoke function takes two parameters.
- The first parameter of Invoke is the name of the function that you want to execute.
- The second parameter of Invoke is the time delay after which you want it to happen.
If we want to call Invoke method repeatedly:
To call Invoke method repeatedly can be done easily with one line of code.
Syntax:
public void InvokeRepeating(string methodName, float time, float repeatTime );
Invoke unity что это
What if you need to invoke a specific code in 2 seconds? You can write an accumulator that counts time, use coroutine to wait for 2 seconds or simply use Invoke or InvokeRepeating methods.
Invoke
Invoke is a public method of MonoBehaviour class (so you can access it from your game scripts). It takes method name and time as parameters and it can be used in that way:
This example executes LaunchProjectile method 2 seconds after starting. It’s just that simple.
InvokeRepeating
InvokeRepeating is very similar to Invoke method but it takes repeat interval as a third parameter, so there can be a difference between the first execution time and any other. Here’s an example:
In this example LaunchProjectile method will be invoked 2 seconds after starting and then in 0.3 second intervals.
CancelInvoke
CancelInvoke allows you to cancel any pending invoke scheduled using two previous methods. It takes a scheduled method name as a parameter.
You may also want to check if the method is scheduled for invocation using IsInvoking method.
Possible alternatives
Invoke methods may be a nice shortcut when you want to quickly schedule a method to be invoked in the future, but it can be difficult to maintain because of passing a string as a method name. Because of that, the refactoring errors will be visible only in the run time and this usually means trouble.
Instead of using Invoke methods you may prefer to use coroutines. Coroutines are lengthy by nature, but a lot safer to maintain (of course if you’re using StartCoroutine overload that takes IEnumerator value type as parameter instead of string).
Unity: A better way to Invoke
Since this article has been released, a lot as changed with Unity and my own knowledge. Therefore I’ve created an updated version of this post, which you can find here.
Unity provides developers with an easy solution to calling a method after a delay. This method is called Invoke . It has a pretty obvious benefit:
- It’s easy to understand and use
But unfortunately, there are far more drawbacks which make this method a candidate for obsoletion.
- It relies on string dependencies, and therefore is prone to typos which may not be caught until runtime
- It does not support parametered methods
- It relies on a distinct method to exist
- It uses reflection to find the method you provide
- You can’t return a value
The problem
Consider the following example:
Let’s go through some of the problems listed above:
- Invoke accepts a string for the method name. This is called a string dependency. String dependencies mean the actual name of the method in code, and the string, are unrelated to each other making refactoring extremely difficult. It is also prone to typos which you will not encounter until you run the game.
- The ChangeColorAfterDelay method cannot accept any parameters. Its logic is fixed, which means if we wanted to change to a different color, we’d have to create another method – creating duplicate code.
- It relies on a method existing in the first place. This does not always make sense. It means that other methods in our class can access this method and that may or may not be what we want to allow. It means we cannot have a single part of the code fire-once-and-forget after a delay.
- Most developers know that reflection is slow. Fetching a method by name is akin to finding an object by its tag. It has to search every method name until it finds a match. This is horribly inefficient.
The only saving grace…
One of these problems can be averted pretty easily. But only one. We can use the nameof operator which will convert a symbol name to a string at compile time. This means if we decide to rename our method using quick-refactor tools, all instances of that name will be changed.
However, this does not change the fact that we are passing a string – which means reflection is being used internally. Besides, we still have the outliers: No parametered methods, no inline invocation, no return values.
A note on coroutines
We have, at our disposal, Unity’s implementation of coroutines. While this is a commonly suggested solution, and does entirely solve the problem of reflection, it still relies on another method existing to run the action – which may or may not be your desired intention.
Of course, you can also make Start itself a coroutine:
That’s seemingly innocuous, right?. “What’s the problem with this?”, I hear you ask. Well, while you can make Start and other fire-once methods a coroutine, you cannot make Update a coroutine:
Which means if you are trying to delay an action from Update , you would still need to create a separate method to act as the coroutine. If you don’t actually need the action to be in a separate method, then this is not good enough.
The solution: Don’t Invoke , await !
In recent times, .NET has introduced the concept of asynchronous programming which is similar to (but often misconstrued as) multi-threading. I’m not going to go into detail about how async / await works – you can read more about that here – but suffice to say that Unity has its own SynchronizationContext which allows async code to run quite smoothly within the engine. We simply have to mark out method as async , and await a Delay :
Yes, this also works with the Update method. In fact, it works with all of the built-in Unity methods! We could just as easily do this:
This also has another added benefit, such that if we wanted to create a separate method for this task, we could pass arguments:
What about InvokeRepeating ?
InvokeRepeating is another common one I see people use. This has all the same problems as Invoke , so I won’t be covering those again.
The alternative is: You decide. There are a couple of ways you can achieve this. I will briefly cover two options:
A simple timer in Update
All we’re doing is checking if the time at which the last change was made, exceeded 2 seconds. If it does, go ahead and perform the action – resetting the last time that the change happened. This works, and is actually a very common solution. Go ahead use this if it satisfies your needs.
Coroutines
Yes, I’m aware. I took a shit on coroutines a few moments ago. But like I said, if it makes sense to delegate the functionality to its own method – this is the better solution.