I'm trying to add a Quest-object to a Person. It succeeds for one and gives a nullreferenceexception for the other, what am I doing wrong here?
P.S. The player and requestor are set in the Unity inspector.
public class GameCreator : MonoBehaviour {
private Quest quest;
public Player player;
public Requestor requestor;
void Start() {
quest = createQuest();
requestor.thisPerson.SetQuest(quest); //this is the problem
player.thisPerson.SetQuest(quest);
}
}
public class Player : MonoBehaviour {
public Person thisPerson;
void Start() {
thisPerson = new Person("Name");
}
}
public class Requestor: MonoBehaviour {
public Person thisPerson;
void Start() {
thisPerson = new Person("Name");
}
}
public class Person {
public Quest quest;
void SetQuest(Quest quest) {
this.quest = quest;
}
}
Any suggestions why this is going wrong?
Move your variable initialization in to Awake(), see the documentation for the following (paraphrased):
Awake is used to initialize any variables or game state before the
game starts.... and use Start to pass any information back and forth.
The way your GameCreator.Start() is written you are reliant on the arbitrary order in which Unity calls your scripts. GameCreator could be the first object called, in which case none of your other scripts have initialized their values.
Other possible errors:
You don't explicitly instantiate requestor, I'm going to assume this was done in Unity's Inspector.
You didn't include `createQuest()' which could be returning null.
As Jordak said, your Start methods can run in any possible order, so you can't rely on Start of some component in the other. You have several ways to address this issue:
You can move the basic initialization code to Awake(). However, this only allows you two levels of initialization, and can be insufficient in the future.
You can adjust script priority in the project settings. However, this is not really C# way, as this makes your code rely on logic that is not obvious from it.
Instead of initializing thisPerson field in the class initialization, create a public property to access it. (Public fields are bad practice in C# anyway). In this property, you can check if the field is null before returning it, and if it is, initialize it.
Related
I'm a total beginner at Unity and I don't understand how to use a variable in two different scripts.
For example, let's say that I have a script called "player" and another called "logic".
In the player script, I create the boolean "IsAlive", and when I collide with something, I die :
public class PlayerScript : MonoBehaviour
{
public bool IsAlive = True;
}
private void OnCollisionEnter2D(Collision2D collision)
{
IsAlive = False;
}
Now, I want to do something in the "Logic" script and have to check if the player is alive or not before. How do I do that ? I tried something like :
public class LogicScript : MonoBehaviour
{
public PlayerScript PlayerScript_logic;
private bool IsAlive_logic = PlayerScript_logic.IsAlive;
}
so that I could use "IsAlive_logic" which would be the same as "IsAlive".
But that is apparently not how if works.
If somebody could help me, please, I'm so lost.
Simply instead of IsAlive_logic in all places use PlayerScript_logic.IsAlive. Despite the fact that you can't access a non-constant field (PlayerScript_logic) when declaring your other fields - it is bad practice to store (and maintain) the same value in multiple places anyway ;)
Alternatively if you really for some reason want/need to you could have a property
private bool IsAlive_logic => PlayerScript_logic.IsAlive;
// or also
//private bool IsAlive_logic { get => PlayerScript_logic.IsAlive; }
// or also
//private bool IsAlive_logic { get { return PlayerScript_logic.IsAlive; } }
which basically simply returns PlayerScript_logic.IsAlive everytime you access it. In general this adds some tiny overhead though and it would be better to go through the PlayerScript_logic.IsAlive directly...
I have two classes: Menu_Buttons, in which there are definitions for methods executed on clicking different buttons in the menu, and PauseMenu, which defines what happens when the Menu key is pressed during the game.
Menu_Buttons:
public class Menu_Buttons : MonoBehaviour
{
public void Menu_NewGameClick()
{
SceneManager.LoadScene(1);
}
public void Menu_ContinueClick()
{
Debug.Log("This will continue the game from the last save");
}
public void Menu_LoadGameClick()
{
SceneManager.LoadScene(1);
Debug.Log("Another menu will show to choose which save to load");
}
public void Menu_SaveGameClick()
{
SaveItem();
Debug.Log("This will save the game");
}
public void Menu_OptionsClick()
{
Debug.Log("This will show the game options");
}
public void Menu_QuitClick()
{
Application.Quit();
Debug.Log("The Game should quit now");
}
}
PauseMenu:
public class PauseMenu : MonoBehaviour
{
//private bool isPauseMenuOpened = false;
public GameObject pauseMenu;
void Update()
{
if (Input.GetKeyDown(KeyCode.B))
{
if (pauseMenu.activeSelf) { ClosePauseMenu(); }
else { OpenPauseMenu(); }
}
}
public void OpenPauseMenu()
{
pauseMenu.SetActive(true);
Cursor.visible = true;
Cursor.lockState = CursorLockMode.Confined;
//isPauseMenuOpened = true;
Time.timeScale = 0f;
}
public void ClosePauseMenu()
{
pauseMenu.SetActive(false);
Cursor.visible = false;
Cursor.lockState = CursorLockMode.Locked;
//isPauseMenuOpened = false;
Time.timeScale = 1f;
}
}
I wanted to add another method called Menu_ResumeClick, which would resume the game from the Pause Menu. Of course, I could just create this method in the PauseMenu script and then everything is fine. It looks like this:
public void Menu_ResumeClick()
{
ClosePauseMenu();
}
But since I would like to keep things organised, I thought it would be better to put this method in the Menu_Buttons script along with all the other similar methods. So I tried this:
public void Menu_ResumeClick()
{
PauseMenu.ClosePauseMenu();
}
And then problems begin... I get an error: an object reference is required for the non-static field method or property. Then if I change any of those classes to static, I get errors saying: cannot declare instance members in a static class. Not to mention that static classes canot inherit from MonoBehaviour. Maybe I would be able to solve those problems somehow, but the thing is I don't want to change the whole code just because I would rather have a method in another class. It's just for keeping things organised, nothing more.
I have to admit that I'm a bit frustrated by how these things work. I can easily put the Menu_ResumeClick() method in the PauseMenu class, but in the future it may be difficult to keep track of things if I have various methods scattered around different scripts. The most reasonable solution is to put every menu button in the Menu_Buttons class and then access them from there, but it poses problems that I described. Actually this is not the first time when I'm having problems with accessing methods or variables from other classes - there always seem to be some difficulties. It seems the best way to write code would be to just have a single class for the whole game because then I would be able to access absolutely anything easily - but again the problem would be with keeping things organised.
So, the question is: can I easily use methods (or variables) from other classes, without changing the whole code for this purpose? In other words can I somehow just call a method from another class like this: className.MethodName(); or set a variable from another class like this: className.varName = 2; without making everything static, etc.?
And a bonus question: If it's not possible, then how should I structure my code? Should I try to squeeze as many things as possible into a single class to be able to access them easily, should I make classes static, whenever it's possible, etc.?
In PauseMenu, you can add a field for the Menu_Buttons, which Unity can serialize, so you can pull the GameObject (what contains the Menu_Buttons) in the inspector, and you can call its public methods (and access its public members) from PauseMenu.
public Menu_Buttons MenuButtons;
// or (I much more like this version, keeping things as encapsulated as possible)
[SerializeField] private Menu_Buttons _menuButtons;
private void Resume() => _menuButtons.Menu_ResumeClick();
Edit based on comments:
Both script can have references to each other. As both logically related, I wouldn't separate them, because with the references, we couple them anyway.
Example:
public class Menu_Buttons : MonoBehaviour
{
[SerializeField] private PauseMenu _pauseMenu;
public void Menu_ResumeClick() => _pauseMenu.ClosePauseMenu();
// ...
}
public class PauseMenu : MonoBehaviour
{
[SerializeField] private Menu_Buttons _menuButtons;
// ...
public void ClosePauseMenu()
{
// ...
}
}
So basically I want to end with several ingame objects, each having few .cs scripts with monobehaviour. (different set of scripts on each object)
party of characters with their skills
Those scripts on each character can vary over time
characters learning new skills/abandoning old
So when the game starts, I want to attach the scripts to objects dynamically at runtime
based on player decision in skill tree
Is there any way how can I do this without using reflection?
EDIT: It seems I found solution how to make it work without reflection
public class TestSkill : MonoBehaviour {}
public class TestFireball : TestSkill {}
public class TestMeleeAttack : TestSkill {}
public class TestSkillBook : MonoBehaviour {
public MonoScript script;
void Start () {
System.Type t = script.GetClass();
TestSkill skill = gameObject.AddComponent(t) as TestSkill;
}
}
I want to attach the scripts to objects dynamically at run-time.
he AddComponent function is used to attach scripts to GameObjects.
Your Object
public GameObject yourgameObject;
Attach script to it:
yourgameObject.AddComponent<YourScript>();
EDIT:
The problem is, I dont know if it will be MyScript1 or MyScript2. I
dont want it to be hardcoded, but modifiable via editor/ingame UI.
I think that you are looking for AddComponent that can take string as param.
There used to be one like this:
public Component AddComponent(string className);
but it was deprecated years ago. I made a new one called AddComponentExt as extension method last year and you can get it here. It can be used like this:
yourgameObject.AddComponentExt<"YourScript">();
You can add script even if it doesn't exist yet. You will get run-time error instead of compile-time error in that case.
Is there any way how can I do this without using reflection?
No, you can't do this without reflection since it doesn't exist yet. That's what reflection is used for.
Since this doesn't fit into the comments of Programmers answer, some example and to clarify on what you can/must do:
// The component to add
public class B : MonoBehaviour
{
public void TestCall()
{
Debug.Log("Success");
}
}
public class A : MonoBehaviour
{
public string ToAddName = "B";
private void Start()
{
System.Type t = System.Type.GetType(ToAddName);
AddComponent(t); // This does successfully add the component (assuming it exists)
Debug.Log(t.GetType()); // This will give out "System.MonoType"
// This doesn't work since it is not known that this is actually "B", not "MonoScript"
GetComponent(t).TestCall();
// What is possible is this, requires hardcoding the method name though:
System.Reflection.MethodInfo mI = t.GetMethod("TestCall");
var c = GetComponent(t);
mI.Invoke(c, null); // null because "TestCall" doesn't take params
}
}
This is not meant to be an actual solution, I'd rather say that there is probably a (better) way to set up your whole construct so that you don't have this problem at all.
So I began learning Swift, but I discovered that I wanted to use Unity3d because it looked interesting to learn, and for games it looked like the better option than Xcode. This meant that I had to learn a new language, however, so I started learning C#. In my project I have 2 classes.
My first Class is LivesDetract. This class is an edge collider. It catches the falling objects, and decreases the life amount:
public class LivesDetract : MonoBehavior {
public int currentLives; //set to 3 in Unity
private int livesDecrementAmnt = 1;
void OnTriggerEnter2D (Collider2D other) {
currentLives = currentLives - livesDecrementAmnt;
}
}
The second class is named GameController. GameController controls the flow of the game. I originally had LivesDetract as a part of GameController, but for organization purposes, I think it should be in its own class. The problem is that I get the following error when I try to inherit from the class LivesDetract:
Error:
"An object reference is required for the non-static field, method, or property 'LivesDetract.currentLives'"
public class GameController : MonoBehavior {
IEnumeratorSpawn () {
while(LivesDetract.currentLives > 0) { // This line is where the error occurs
//Game Actions Occur
}
}
}
I think I have provided enough information, but if more is needed let me know.
In Swift I was able to set the function as a variable:
var livesDetract = LivesDetract()
I could then use:
while livesDetract.currentLives > 0 {
}
That doesn't seem to work in C# though.
You are trying to access currentLives without instantiating the object. You need find the object in Unity before making use of it.
In order to get variable(s), function(s) in another class, I have known 2 ways of doing this. First, is to use Get Component to the Script that we want to get the variable(s), function(s) into. Second, is to use Instance of the Script itself.
So I have made the following code:
First case: Get Component to the Script itself
public class Manager : MonoBehaviour
{
private AnotherManager _anotherManager;
private void Awake()
{
_anotherManager = GameObject.Find("Managers").GetComponent<AnotherManager>();
}
private void Start()
{
_anotherManager.myIntVariable = 10;
_anotherManager.MyFunction();
}
}
public class AnotherManager : MonoBehaviour
{
public int myIntVariable;
public void MyFunction()
{
}
}
Second case: Use Instance of the Script itself
public class Manager : MonoBehaviour
{
private void Start()
{
AnotherManager.instance.myIntVariable = 10;
AnotherManager.instance.MyFunction();
}
}
public class AnotherManager : MonoBehaviour
{
public static AnotherManager instance;
public int myIntVariable;
private void Awake()
{
instance = this;
}
public void MyFunction()
{
}
}
My question is: Is there any difference between those cases? In terms of good practice of coding for programmer or performance or it is just a matter of programmer's perspective or whatever else?
Thanks
The second example is the what is known as the Singleton Pattern and should be used very sparingly.
I try to never use the first approach either where you find the gameobject and hope it exists.
You can expose a field for the Unity Inspector so that you can wire it up the same as you can expose any other variable
public AnotherManager AnotherManager;
Alternatively, if you hate using public all over the place like that, like me, you can also indicate to Unity that you wish to expose this variable in the inspector with the SerializeField attribute
[SerializeField]
private AnotherManager anotherManager;
With both of these methods, you can then drag an an object that has the AnotherManager component attached into the field in the inspector.
If instantiated objects need access to this, you will need to wire it up when it is instantiated.
If you need help attaching it in unity I can attach some screenshots.