Is there anyway to create a Scala class which is an object Array , that has an undefined number of objects in the array.
for example I can do what I want using a var
var River1 = new ArrayBuffer[RiverReach]
River1.+=(rr1,rr2,rr3)
and this works fine but i'd like a class so I can add a bunch of methods to it.At the moment I can manually add arguments in the () but the number could vary depending on the Objects. Is there a way to not set a limit? Bit of context I'm a scala beginner and i'm learning via udemy courses at the moment so please bear with me. Any help would be appreciated
Current setup. I've used ArrayBuffer as its mutable and i'll want to sum values from all the elements in the array to the head. But thats a question for a different page.
class River[T>:ArrayBuffer[RiverReach]]() {
//bunch of methods
}
You can wrap the buffer into River, redirect River's += and other methods to the buffer, then add all the other functions you need, for example:
case class RiverBeach(altitude: Int)
class River {
private val buffer = new ListBuffer[RiverBeach]()
def +=(riverBeach: RiverBeach): River = {
buffer += riverBeach
this
}
def ++=(riverBeach: RiverBeach*): River = {
buffer ++= riverBeach
this
}
def size: Int = buffer.size
// your methods
}
val river = new River()
river += RiverBeach(1)
river ++= (RiverBeach(2), RiverBeach(3), RiverBeach(4))
println(river.size) // 4
Mike Allens idea was correct, after more reading better solution is to simply extend Arraybuffer
class River extends Arraybuffer[RiverReach] {
//bunch of methods
}
Related
I have many class in my library almost 300, and I want to generate instance name by loop. In other words I wanna instead of this approach(witch has many code line):
X:This is my problem:
var cm1: Cm1 = new Cm1();
var cm2: Cm2 = new Cm2();
var cm3: Cm3 = new Cm3();
...
use like this approach (less than 10 code lines):
Y:I think this is solution:
for (var i: uint = 1; i < 4; i++)
{
var getChildByName("cm" + i): getChildByName("Cm" + i) = new getChildByName("Cm" + i);
}
but I know above code does not work, is there any way to make them !
-What am I actually trying to solve?
Make many variable by a few line code and save time and size app!
-Why do I have ~300 classes and why are you trying to create them in a loop at once?
This is about to data of request application!
-What do these classes do that you unconditionally need one of each all at the same time?
Because those data would show at first time!
First, it is better to store the classes in an Array or Object rather than an external variable for each item. if you want to access them by name, better to use object:
var classList:Object=new Object();
Then in your loop:
for(var i:uint=1;i<NumberOfClasses;i++){
classList["cm"+i.toString()]=new (getDefinitionByName("Cm"+i.toString()) as Class)();
}
getDefinitionByName is used to make Constructors using String;
Note: if your classes contain a package directory, you should include it. for example:
getDefinitionByName("myclasses.cm.Cm123")();
Then you can access them using Bracket syntax:
classList["cm123"].prop=val;
And don't forget to:
import flash.utils.getDefinitionByName;
I Hope it will help.
EDIT
to use Array instead of object, the loop should be:
for(var i:uint=1;i<NumberOfClasses;i++){
classList[i]=new (getDefinitionByName("Cm"+i.toString()) as Class)();
}
then to access them:
addChild(classList[0]);//0 or any other index;
I am currently learning swift and am experimenting with data structures. In may code I have certain routines with a name(String) and several tasks(Array of Strings). These values are in a structure.
So I am trying to add another value to the array after it has been initialized. My code is actually working, however I really think it very weird and odd and DO NOT think, that it is the way it should be done.
var routineMgr: routineManager = routineManager();
struct routine{
var name = "Name";
var tasks = [String]();
}
class routineManager: NSObject {
var routines = [routine]();
func addTask(name: String, desc: String){
//init routines with name and an array with certain values, here "Hallo" & "Moin"
routines.append(routine(name: name, tasks: ["Hallo","Moin"]));
//so i just put this part here to make the example shorter, but it would be in ad different function to make more sense
//adding a new value ("Salut") to the tasks array in the first routine
//getting current array
var tempArray = routines[0].tasks;
//appending new value to current value
tempArray.append("Salut");
//replacing old routine with a copy (same name), but the new array (with the appended salut)
routines[0] = routine(name: routines[0].name, tasks: tempArray);
}
}
I have tried some (to me) "more correct" ways, like:
routines[0].tasks.append("Salut");
But I always got tons of errors, which I also did not understand.
So my question now: How is it actually done correctly? And why does the second way not work?
Your help and advice is really appreciated!
You can create a function to append the values in the struct (that is what I would do). You can even use it to validade values or anything else you need to do before append, it can also return a boolean to let your code know if the value was successfully appended or not
var routineMgr: routineManager = routineManager();
struct routine{
var name = "Name";
var tasks = [String]();
mutating func addTask(task: String){
tasks.append(task)
}
}
class routineManager: NSObject {
var routines = [routine]();
func addTask(name: String, desc: String){
routines.append(routine(name: name, tasks: ["Hallo","Moin"]));
routines[0].addTask("Salut")
}
}
I hope that helps
From array.scala of scala-2.10.4, The Array is defined as
final class Array[T](_length: Int) extends java.io.Serializable with java.lang.Cloneable {
/** The length of the array */
def length: Int = throw new Error()
def apply(i: Int): T = throw new Error()
def update(i: Int, x: T) { throw new Error() }
override def clone(): Array[T] = throw new Error()
}
Please note, the apply method will throw an exception! And for the accompany object Arrry, I find the following codes:
def apply[T: ClassTag](xs: T*): Array[T] = {
val array = new Array[T](xs.length)
var i = 0
for (x <- xs.iterator) { array(i) = x; i += 1 }
array
}
I know there is an implicit parameter which is ClassTag[T], what make me surprised is how
new Array[T] (xs.length)
is compiled. By decompiling the Array.class, I find that line is translated to :
public <T> Object apply(Seq<T> xs, ClassTag<T> evidence$2)
{
// evidence$2 is implicit parameter
Object array = evidence$2.newArray(xs.length());
...
}
I am really confused by this kind of translation, what is the rule under the hood?
Thanks
Chang
The Scala Array Class is just a fake wrapper for the runtime so you can use arrays in Scala. You're probably confused because those methods on the Array class throw exceptions. The reason they did this is so that if you actually end up using the fake class it blows up since really it should be using the java runtime array, which does not have a proper container class like Scala. You can see how the compiler handles it here. When your using arrays in Scala you're probably also using some implicits from predef like ArrayOps and WrappedArray for extra helper methods.
TLDR: Scala compiler magic makes arrays work with the java runtime under the hood.
On the JVM arrays are exempt from type-erasure, e.g. at runtime instead of Array[_] there is a difference between Array[Int], Array[String] and Array[AnyRef] for example. Unlike Java, Scala can handle this mostly transparently, so
class Foo {
val foo = new Array[Int](123)
}
has a direct byte-code invocation for creating the integer array, whereas
class Bar[A](implicit ev: reflect.ClassTag[A]) {
val bar = new Array[A](123)
}
is solved by using the implicit type evidence parameter of type ClassTag[A] so that at runtime the JVM can still create the correct array. This is translated into the call you saw, ev.newArray(123).
Let's say I have an array, each item in the array has a corresponding library item.
I'd like to do something like :
var rando = Math.round(Math.random()*3)
var myArray = new Array ["ball", "wall", "fall"]
var i:myArray[rando] = myArray[rando] new myArray[rando]()
addChild(i)
But, this doesn't work. What's the secret?
Thank You,
Victor Hugo
Surprised no one mentioned getDefinitionByName() here.
Here's some complete code to get your example working:
var myArray = ["ball", "wall", "fall"];
/**
* Creates a random instance based on an input array containing class names as Strings.
* #param The input array containing aforementioned Strings.
* #return The newly created instance.
*/
function createRandom(typeArray:Array):*
{
// Select random String from typeArray.
var selection:String = typeArray[ int(Math.random() * typeArray.length) ];
// Create instance of relevant class.
var Type:Class = getDefinitionByName(selection) as Class;
// Return created instance.
return new Type();
}
// Randomly create and add instance.
var instance:DisplayObject = createRandom(myArray);
addChild(instance);
Ok so there are a bunch of problems with this.
A large one being var i:myArray[rando] = myArray[rando] new myArray[rando]() not really too sure what you're trying to do here.
Anyway I'm going to assume ball, wall and fall are instance names of MovieClips you have in your library. I think you're going to want something like this
var rando:int = Math.floor(Math.random()*3); //As the comments point out this should give you a random
//int between 0 and 2, arrays are 0 indexed so this is what we want if we have 3 items
Now for your array, you're current putting strings in there. Flash has no idea what "ball", etc are.
Try something like this
var myArray:Array = new Array [new ball(), new wall(), new fall()]; //this creates a new instance of your library object and stores it in your array
Now to add one of these to your stage:
addChild(myArray[rando]); //this uses the random number to pull one of the items out of your array
What you're trying to do with var i:myArray[rando] doesn't really make sense. There is no type of myArray[rando] this slot should be holding a MovieClip
If you only have a few choices, it's easier to use a switch-case.
switch (rando) {
case 0:
i = new ball();
break;
case 1:
i = new wall();
break;
case 2:
i = new fall();
break;
}
addChild(i);
I suggest you define the variable i as a MovieClip, in which case it can be instantiated as both ball, wall, fall.
Given that ball, wall and fall are in the library exported to actionscript.
Just guessing off your limited information but give this a shot.
private function myFunction():void{
var rando = Math.round(Math.random()*3);
var myArray= new Array ["ball", "wall", "fall"];
}
private function generateItem(item:String):void{
switch(item){
case "ball" : generateBall(); break;
case "wall" : generateWall(); break;
case "fall" : generateFall(); break;
}
private function generateBall():void{
//code to generate ball
addChild(ball);
}
private function generateFall():void{
//code to generate fall
addChild(fall);
}
private function generateWall():void{
//code to generate wall
addChild(wall);
}
Change your arrary line to:
var myArray = new Array [ball, wall, fall];
This should work. :)
Marty Wallace gets big praise for steering me down the path of getDefinitionByName(). The example he posted was good, but this example does exactly what I was going for.
http://www.emanueleferonato.com/2011/03/31/understanding-as3-getdefinitionbyname-for-all-eval-maniacs/
I want to find a way to only allow certain objects into an array that have a certain word in thier class name. Or at least find the optimal way of doing something like this. Heres the details. I have an Array that stores all the objects dropped into a cart.
function addProductToArray (e:MouseEvent):void{
currMC = (e.target as MovieClip);
myCart.itemsInCart.push(currMC);
trace(myCart.itemsInCart);}
If, for example, I drop an [object BreadGrain] and a [object PastaGrain].
trace(myCart.itemsInCart);// would trace [object BreadGrain],[object PastaGrain].
Easy, no problems there. But what do I do if I only want to allow 2 objects with "Grain" in their Classname into the array? I want to do this so that the user can only drop 2 of each type of food into the 'cart'. The types of food are Grain, Fruit, Vegetable, Meats etc and I've appended the type of food to the end of the Classname, hopefully so that I can use it to detect what type of food it is and stop it from being added over the limit as well as displaying an error. i.e "You already have 2 Grain products".
I hope that makes sense. Anyway, i've found that works well to a degree:
if (currMC is BreadGrain) {
myCart.itemsInCart.push(currMC);
} else {
// error message code here
}
BUT I have several products and I don't want to have to write a if/else or switch statement for them all. I was hoping to do this dynamically with something similar to:
//this is an example of the logic
if (currMC classNameContainsTheWord "Grain" AND myCart.itemsInCart DoesNotContainMoreThan 2 Grain Objects) {
myCart.itemsInCart.push(currMC);
} else {
// error message code here
}
I'm stumped. Even just a "Dude, you are doing this all wrong" would help. Thanks.
You can get the class name of any object with the getQualifiedClassName function. Then you could try to match strings agains a certain pattern, with a RegExp or you could also just check if the class name contains some substring.
That said, I think a better approach could be using either a common base class or an interface.
// assuming your objects extend MovieClip
public class Grain extends MovieClip{
public function Grain() {
super();
}
public function someCommonMethodToAllGrains():void {
}
}
or
// It's customary to prefix interfaces name with an "I" in AS;
// I'm not doing it here so the code works for both a base class and an interface
public interface Grain {
function someCommonMethodToAllGrains():void;
}
Then, if you went with the base class:
public class BreadGrain extends Grain {
public function BreadGrain() {
super();
}
override public function someCommonMethodToAllGrains():void {
// if this makes sense for your object...
super.someCommonMethodToAllGrains();
}
}
public class PastaGrain extends Grain {
public function PastaGrain() {
super();
}
override public function someCommonMethodToAllGrains():void {
// if this makes sense for your object...
super.someCommonMethodToAllGrains();
}
}
Or, with the interface
public class BreadGrain extends MovieClip implements Grain {
public function BreadGrain() {
super();
}
public function someCommonMethodToAllGrains():void {
}
}
public class PastaGrain extends MovieClip implements Grain {
public function PastaGrain() {
super();
}
public function someCommonMethodToAllGrains():void {
}
}
If these objects are MovieClips, perhaps it's less tedious to use a base class, because otherwise you'd have to cast your objects back to MovieClip (or DisplayObject) any time you want to add them to the display list (or remove them). By the way, that's because someone at Adobe forgot to include an IDisplayObject interface and have the display list API accept objects that implemented this interface instead of a half-assed abstract class that you can't derive directly anyway (a.k.a. DisplayObject); this would have make it easier to treat display objects as interfaces, but I digress).
Anyway, either with an interface or a common base class you could do your validation with the is operator, but you'd just have to check for one type: Grain.
if(theObject is Graing && theArray.lenght <= 2) {
theArray.push(theObject);
}
You could also take this further and use a Vector instead of an Array. A Vector works almost the same as an Array, but it's strictly typed, so you could do:
var items:Vector.<Grain> = new Vector.<Grain>();
items.push(grainObject);
You'll get a compile time error if you try to add an object that does not extend/implement Grain.
Vectors are available for Flash Player 10 and you'd need Flash CS4, though (if you're using the Flash IDE; otherwise, I think you'd need at least the 3.2 SDK to compile).
Hm. I think you're going to need something a bit more complex to make this work properly. You're actually asking a two-part question: how to keep track of stuff, and how to identify stuff. I'll start with the easy bit, keeping track.
DISCLAIMER: My AS3 is pretty rusty, but at least the theory should be sound, even if the implementation might be a bit off.
First, you'd want to define the limits for each type of food, thus:
var dctLimits = new Object(); // not really a Dictionary, but we'll use it like one
dctLimits[ "grain" ] = 3;
dctLimits[ "meat" ] = 5;
...
Then, you want to keep count of objects you're adding to your cart
var dctCount = new Object();
dctCount[ "grain" ] = 0;
dctCount[ "meat" ] = 0;
...
Then, when you add a new object, first check its type against the relevant count. If the counter is less than the limit, let it in and increment the counter:
var type:String = getFoodTypeForObject( currMc );
if( dctCount[ type ] < dctLimit[ type ] ){
items.push( currMc );
dctCount[ type ]++;
} else {
// throw error
}
You'll notice that I've created an imaginary function, getFoodTypeForObject(). This is the trickier bit: identification.
You could implement your example logic like so:
function getFoodTypeForObject( currMc ){
if( getQualifiedClassName( currMc ).indexOf( "Grain" ) > -1 ){
return( "grain" );
} else if( getQualifiedClassName( currMc ).indexOf( "Meat" ) > -1 ){
return( "meat" );
}
...
}
Where classNameContainsTheWord is achieved with a combination of getQualifiedClassName and indexOf, but better would be to use a common base class, as suggested by Juan Pablo Califano. I'd suggest a slightly different style though:
public class CartItem extends MovieClip{
public var isGrain:Boolean;
public var isMeat:Boolean;
public function CartItem() {
super();
}
}
use that as the base Class for your cart item MCs, then set those boolean properties on the instances of MCs on your stage. Then, you can detect the type of something like this:
function getFoodTypeForObject( object ){
if( object.isGrain ){
return( "grain" );
} else if( object.isMeat ){
return( "meat" );
}
...
}
Cleaner than all that classname business, and has the added benefit that you can set something's properties independent of its class name.
It's not perfect; for instance, you'd need something more advanced if you needed a lot of properties, but it should be enough for you to keep going.
Uni had me doing other stuff for a while but finally I can get back into my game project.
I've got it working. I used Juan Pablo Califano's method. I did initially use Henry Cooke's because I wanted to get away with making a .AS file for each food (i.e. apple.as, cereal.as, bread.as, oranges.as). With Henry Cooke's method I created a
`var foodTypeLimit:Object = new Object();
foodTypeLimit["grain"]=2;
foodTypeLimit["fruit"]=2;
And var foodTypeCount:Object = new Object();
etc etc
`
For each food type. Then used the:
var type:String = getFoodTypeForObject( currMc );
if( foodTypeCount[ type ] < foodTypeLimit[ type ] ){
items.push( currMc );
foodTypeCount[ type ]++;
} else {
// throw error
}
As suggested. The function returned the string and viola it worked fine. However because my foodTypeCount variables (for example foodTypeCount["grain"]=0;) was inside the function, every time the function called these were set to 0 so the increment never got above with each call. So I thought, ok, i'll put these foodTypeCount variables outside of the function along with the instantiation of the var foodTypeCount:Object = new Object(); BUT NO, I kept getting the:
Error #1120: Access of undefined property foodTypeObject.
Even though it was right under the freakin declaration. I get i'm just too noob to understand why this is so. Anyway, for this reason (the lack of incrementation, which was essential to this function) I bit the bullet and used Juan Pablo Califano's way.
First I wrote out the classes like so:
public class Bread extends MovieClip implements Grain {
public function Bread() {
super();
}
public function someCommonMethodToAllGrains():void {
}
}
And then added the interface
`public interface Grain {
function someCommonMethodToAllGrains():void;
}
`
And now my function looks something like this:
if(currMC is Grain){
if(grainCount<2){
addProductToBasket();
grainCount++;
} else {
notAllowed("Grain");
}
}
function addProductToBasket(){
removeChild(currMC);
basketArray.push(currMC);
//remove listeners set mc to null etc
}
function notAllowed(foodType:String){
error.text="Sorry but you already have 2"+foodType+"products";
}
I tried to put all this into a switch. For example:
switch(currMC){
case is Grain:
//do this
break;
}
The above implementation didn't work. Perhaps switch statements probably aren't meant to be used that way. idk. :S
Anyway, thanks for the really great answers guys, this is my favorite site to come to for answers to life the universe and everything.