I'm new to unity and am having a bit of trouble getting my head around the architecture.
Lets say I have a C# script component called 'component A'.
I'd like component A to have an array of 100 other components of type 'component B'.
How do I construct the 'component B's programmatically with certain values?
Note that 'component B' is derived from 'MonoBehaviour' as it needs to be able to call 'StartCoroutine'
I'm aware that in unity you do not use constructors as you normally would in OO.
Note that 'component B' is derived from 'MonoBehaviour' as it needs to
be able to call 'StartCoroutine'
I'm aware that in unity you do not use constructors as you normally
would in OO.
That's true. A possibility is to istantiate components at runtime and provide a method to initialize them ( if initialization requires arguments, otherwise all initialization can be done inside Start or Awake methods ).
How do I construct the 'component B's programmatically with certain
values?
Here's a possible way:
public class BComponent : MonoBehavior
{
int id;
public void Init(int i)
{
id = i;
}
}
}
public class AComponent : MonoBehavior
{
private BComponent[] bs;
void Start()
{
bs = new BComponent[100];
for (int i=0; i < 100; ++i )
{
bs[i] = gameObject.AddComponent<BComponent>().Init(i);
}
}
}
Note that in the example above all components will be attached to the same GameObject, this might be not what you want. Eventually try to give more details.
Related
I'm a beginner learning dart from the book dart apprentice and I reached where they were discussing constructors in dart classes, the book was implying that constructors create instances of the class which I understood but I needed more info about constructors. So I googled and some results repeated what was already in the book about it being used to create instances of a class while others also showed that it's used to instantiate class properties, but my problem is with the other answer which I found that they are used to instantiate properties of a class, but my question is: I instantiate all class properties when I create the class by declaring the property variables, like this:
class UserClass{
userClassProperty = "";
anotherUserClassProperty = ""; }
why is the constructor also needed to instantiate class properties?
Often, values are unique to every class instance.
Consider the following example:
class Point {
final int x;
final int y;
const Point(this.x, this.y);
double get distanceToOrigin => sqrt(x * x + y * y);
}
If the x and y values were defined inside the class, it would be pretty useless. Instead, different Point objects can be instantiated with different values, which means the same code can be used for different situations.
Ok, so constructors instantiate or start a class by collecting all the data the class needs to start to start working. Constructors are so important that the dart compiler provides one even if you don't explicitly create one. For example, you create a class for mammals like this :
class Mammal{
String name = "cat";
int numberOfLegs = 2;
}
Although you don't explicitly add a constructor the dart compiler adds a default constructor like this :
class Mammal{
Mammal(); //This is added by dart during the class instantiation by default.
String name = "cat";
int numberOfLegs = 2;
}
Yeah, that's how crucial constructors are to the dart compiler.
And on the topic of why are they necessary even when you declare all the properties by yourself in the class, as hacker1024 said it would make the class pretty useless, as the point of the existence of classes is to create variants but with different properties. Not adding a constructor to your class and defining all the properties in the class would mean that your class doesn't take property arguments which in turn also means that different variants of your class can't be created. Again this goes directly against the point of the existence of dart classes. For example, you have a class like this :
class Mammals{
Strig name = "Human";
int numberOfLegs = 2;
bool hasFur = false;
}
final cat = Mammal();
final human = Mammal();
print(cat.numberOfLegs); //Prints 2
//2
print(human.numberOfLegs); //Also prints 2
//2
print(cat.hasFur);
// false
Yeah, this class is problematic. Cats with 2 legs? You would agree with me that that's not how things are in reality. And also the class is pretty useless in the sense that it's not modular, no matter which kind of mammal we create be it a cat, a sheep or even a cow the name property is going to be the default one we set, that is "Human". When we create a class to simulate mammals we want to be able to define what kind of properties it has, not use some fixed values. So you want to create a class which has a constructor like this :
class Mammals{
Mammals(String name,int noOfLegs, bool hasFur){
this.name = name;
this.noOfLegs = noOfLegs;
this.hasFur = hasFur;
}
String name = "";
int noOfLegs = 0;
bool hasFur = False;
}
final cat = Mammal("Cat", 4, True); //Now you can pass in the properties ou want.
final human = Mammal("Human", 2, false);
print(cat.name); //This prints the customized name of the object cat instead of some fixed value
//Cat
print(human.name); //This prints the customized name of the object human
Now we have two instances of the class with separate property values.
Although this adds a little more code, the modularity benefit is worth it.
new to unity so please ignore if I sound stupid.
I have to scripts references in a script. Example, script A and B are referenced in script C.
I need to store script A and B variable names in a another variable so that I can use that variable in conditioning.
private FemalePlayerAnimations femalePlayerAnimations;
private MalePlayerAnimations malePlayerAnimations;
private Variable variable; // Got Problem Here
void Awake()
{
femalePlayerAnimations = GetComponent<FemalePlayerAnimations>();
malePlayerAnimations = GetComponent<MalePlayerAnimations>();
}
void Start()
{
if(1 + 1 = 2) // Some Condition
{
variable = femalePlayerAnimations;
}
else if(1 + 2 = 3) // Some Another Condition
{
variable = malePlayerAnimation;
}
}
Thanks in advance.
If I understand your question correctly, you'll need to use inheritence and have your male/female animations inherit from the same base class.
i.e.
public abstract class BasePlayerAnimator : MonoBehavior {}
public class MalePlayerAnimator : BasePlayerAnimator {}
public class FemalePlayerAnimator : BasePlayerAnimator {}
Real question though is why do you need two different classes for male/female animations? wouldn't a single class with 2 different instances cover your needs?
I have a feeling you don't simply want the name of the variable as a string.
The logic you are trying to implement here won't work. You can't have a variable that holds the FemalePlayerAnimations class hold a MalePlayerAnimations class.
You should reconsider the design of your program as you can have two different instances (prefabs) of the same theoratical PlayerAnimations class. This is how Animation Controllers work in Unity.
Alternatively you could use a boolean field to store states, for example: bool useFemaleAnimations that is changed in the conditions and implement the correct "script" where applicable.
I'm looking to create a .NET application which calls various matlab functions to process some data. What I want to do is have a single class where multiple functions can access the same variables. Below is some pseudocode of what I would like to do. I want to call one function that sets a variable, and another function that returns the value of the variable.
class TestClass
{
int x;
public void SetX(int new_x)
{
x = new_x;
}
public int GetX()
{
return x;
}
}
Using Matlab Compiler SDK, I know that I can call individual functions, but is there a way multiple functions will be able to interact with the same variable like the above functions?
I often need to pass invalid location to functions that optionally can use location (eg. RTS unit action). But this does not compile:
public abstract void CastSpell(Spell spell, Vector3 targetLocation = null);
So how can I make a proper invaid Vector3 to determine invalid/"don't care" locations? I've seen things like vector with -999999 coordinates - but that's a nasty trick that might cause bugs (eg. on huge maps).
I had a similar problem in the past, I found there was two solutions. The first solution was to create a wrapper for the class.
Class Vector3Wrapper
{
Vector3 vector;
}
Then I would simply set the Vector3Wrapper to null then if it wasnt null access its vector. A better method would be making it a Nullable type. A example is below.
http://unitypatterns.com/nullable-types/
public class Character : MonoBehaviour
{
//Notice the added "?"
Vector3? targetPosition;
void MoveTowardsTargetPosition()
{
//First, check if the variable has been assigned a value
if (targetPosition.HasValue)
{
//move towards targetPosition.Value
}
else
{
//targetPosition.Value is invalid! Don't use it!
}
}
(note: this is related to Usage preference between a struct and a class in D language but for a more specific use case)
When writing a D interface to, say, C++ code, SWIG and others do something like this:
class A{
private _A*ptr;//defined as extern(C) elsewhere
this(){ptr=_A_new();}//ditto
this(string s){ptr=_A_new(s);} //ditto
~this(){_A_delete(ptr);} //ditto
void fun(){_A_fun(ptr);}
}
Let's assume no inheritance is needed.
My question is: wouldn't it be preferable to use a struct instead of a class for this?
The pros being:
1) efficiency (stack allocation)
2) ease-of-use (no need to write new everywhere, eg: auto a=A(B(1),C(2)) vs auto a=new A(new B(1),new C(2)) )?
The cons being:
require additional field is_own to handle aliasing via postblit.
What would be the best way to do so?
Is there anything else to worry about?
Here's an attempt:
struct A{
private _A*ptr;
bool is_own;//required for postblit
static A opCall(){//cannot write this() for struct
A a;
a.ptr=_A_new();
a.is_own=true;
return a;
}
this(string s){ptr=_A_new(s); is_own=true;}
~this(){if(is_own) _A_delete(ptr);}
void fun(){_A_fun(ptr);}
this(this){//postblit;
//shallow copy: I don't want to call the C++ copy constructor (expensive or unknown semantics)
is_own=false; //to avoid _A_delete(ptr)
}
}
Note the postblit is necessary for cases when calling functions such as:
myfun(A a){}
I suggest that you read this page. The only functions on C++ classes that you can call in D are virtual functions. That means that
D cannot call C++ special member functions, and vice versa. These include constructors, destructors, conversion operators, operator overloading, and allocators.
And when you declare a C++ class in D, you use an extern(C++) interface. So, your class/struct would look like this
extern(C++) interface A
{
void fun();
}
However, you'd need another extern(C++) function to allocate any objects of type A, since it's C++ code that has to do that as the D code doesn't have access to any of the constructors. You'd also need a way to pass it back to C++ code to be deleted when you're done with it.
Now, if you want to wrap that interface in a type which is going to call the extern(C++) function to construct it and the extern(C++) function to delete it (so that you don't have to worry about doing that manually), then whether you use a class or struct depends entirely on what you're trying to do with it.
A class would be a reference type, which mirrors what the C++ class actually is. So, passing it around would work without you having to do anything special. But if you wanted a guarantee that the wrapped C++ object was freed, you'd have to do so manually, because there's no guarantee that the D class' finalizer would ever be run (and presumably, that's where you'd put the code for calling the C++ function to delete the C++ object). You'd have to either use clear (which will actually be renamed to destroy in the next release of the compiler - dmd 2.060) to destroy the D object (i.e. call its finalizer and handle the destruction of any of its member variables which are value types), or you'd have to call a function on the D object which called the C++ function to delete the C++ object. e.g.
extern(C++) interface A
{
void fun();
}
extern(C++) A createA();
extern(C++) void deleteA(A a);
class Wrapper
{
public:
this()
{
_a = createA();
}
~this()
{
deleteA(_a);
}
auto opDispatch(string name, Args...)(Args args)
{
return mixin("_a." ~ name ~ "(args)");
}
private:
A _a;
}
void main()
{
auto wrapped = new Wrapper();
//do stuff...
//current
clear(wrapped);
//starting with dmd 2.060
//destroy(wrapped);
}
But that does have the downside that if you don't call clear/destroy, and the garbage collector never collects your wrapper object, deleteA will never be called on the C++ object. That may or may not matter. It depends on whether the C++ object really needs its destructor to be called before the program terminates or whether it can just let its memory return to the OS (without its destructor being called) when the program terminates if the GC never needs to collect the wrapper object.
If you want deterministic destruction, then you need a struct. That means that you'll need to worry about making the struct into a reference type. Otherwise, if it gets copied, when one of them is destroyed, the C++ object will be deleted, and the other struct will point to garbage (which it will then try and delete when it gets destroyed). To solve that, you could use std.typecons.RefCounted. Then you get something like
extern(C++) interface A
{
void fun();
}
extern(C++) A createA();
extern(C++) void deleteA(A a);
struct Wrapper
{
public:
static Wrapper opCall()
{
Wrapper retval;
retval._a = createA();
return retval;
}
~this()
{
if(_a !is null)
{
deleteA(_a);
_a = null;
}
}
auto opDispatch(string name, Args...)(Args args)
{
return mixin("_a." ~ name ~ "(args)");
}
private:
A _a;
}
void main()
{
auto wrapped = RefCounted!Wrapper();
//do stuff...
}
You could also define the wrapper so that it has the ref-counting logic in it and avoid RefCounted, but that would definitely be more complicated.
Regardless, I would definitely advise against your suggestion of using a bool to mark whether the wrapper owns the C++ object or not, because if the original wrapper object gets destroyed before all of the copies do, then your copies will point to garbage.
Another option if you did want the C++ object's copy constructor to be used (and therefore treat the C++ object as a value type) would be to add an extern(C++) function which took the C++ object and returned a copy of it and then use it in a postblit.
extern(C++) A copyA(A a);
this(this)
{
if(_a !is null)
_a = copyA(a);
}
Hopefully that makes things clear enough.