Extending a class in another file - class

I have some TypeScript code that is being generated by a tool. I'd like to extend this class in another file. As of 0.9.1.1, what's the best way to go about this?
I thought maybe I could staple my additional functions onto the prototype, but this is giving various errors (which change depending what mood the compiler is in).
For example:
Foo.ts (generated by a tool)
module MyModule {
export class Dog { }
}
Bar.ts
module MyModule {
function bark(): string {return 'woof';}
Dog.prototype.bark = bark;
}

You cannot split a class definition between multiple files in TypeScript. However typescript understands how JavaScript works and will let you write idomatic JavaScript classes just fine:
module MyModule {
export function Dog(){};
}
module MyModule {
function bark(): string {return 'woof';}
Dog.prototype.bark = bark;
}
Try it online
One way around this is to use inheritance:
class BigDog extends Dog{
bark(){}
}

I have encountered your problem as well before, but I had some deeper problems. You can see from basarat's example, that simple functions can be added as an extension to the prototype, but when it comes to static functions, or other static values you might want to extend your (presumably third party) class, then the TSC will warn you, that there is no such method defined on the class statically.
My workaround was the following little hack:
module MyModule {
export function Dog(){};
}
// in the other file
if (typeof MyModule !== 'undefined'){
Cast<any>(MyModule.Dog).Create = ()=>{return new Dog();};
}
// where Cast is a hack, for TS to forcefully cast types :)
Cast<T>(element:any):T{ return element; }
This should cast MyModule.Dog, to an any object, therefore allowing attachment of any kinds of properties, functions.

Related

Better way to do class type alias?

From time to time, I would like to call a class differently depending on the context or to reduce duplication.
Let's assume, I have the following classes defined:
// in file a.dart
class A {
final String someprop;
A(this.someprop)
}
// in file b.dart
abstract class BInterface {
String get someprop;
}
class B = A with EmptyMixin implements BInterface;
For this syntax to check out, I have to define EmptyMixin so that the syntax is OK.
Do you know of a better/prettier way to do this "aliasing" in Dart?
I'm afraid the way you're doing it is the prettiest way to do this at the moment. There is a very old, but still open and active issue: https://github.com/dart-lang/sdk/issues/2626 that proposes the typedef B = A; syntax for aliasing types.

AngelScript - Avoid implicit default constructor from running

I'm currently testing some simple AngelScript stuff, and noticed something I find a bit strange when it comes to how objects are initialized from classes.
Let's say I define a class like this:
class MyClass {
int i;
MyClass(int i) {
this.i = i;
}
}
I can create an object of this class by doing this:
MyClass obj = MyClass(5);
However it seems I can also create an object by doing this:
MyClass obj;
The problem here is that obj.i becomes a default value as it is undefined.
Additionally, adding a default constructor to my class and a print function call in each one reveals that when I do MyClass obj = MyClass(5); BOTH constructors are called, not just the one with the matching parameter. This seems risky to me, as it could initialize a lot of properties unnecessarily for this "ghost" instance.
I can avoid this double-initialization by using a handle, but this seems more like a work-around rather than a solution:
MyClass# obj = MyClass(5);
So my question sums up to:
Can I require a specific constructor to be called?
Can I prevent a default constructor from running?
What's the proper way to deal with required parameters when creating objects?
Mind that this is purely in the AngelScript script language, completely separate from the C++ code of the host application. The host is from 2010 and is not open-source, and my knowledge of their implementation is very limited, so if the issue lies there, I can't change it.
In order to declare class and send the value you choose to constructor try:
MyClass obj(5);
To prevent using default constructor create it and use:
.
MyClass()
{
abort("Trying to create uninitialized object of type that require init parameters");
}
or
{
exit(1);
}
or
{
assert(1>2,"Trying to create uninitialized object of type that require init parameters");
}
or
{
engine.Exit();
}
in case that any of those is working in you environment.
declaring the constructor as private seems not to work in AS, unlike other languages.

Is there a way around to create TypeScript classes in closures?

I'm using IntelliJ IDEA's File Watcher to automatically compile the TypeScript files, but for some reason it's not liking classes defined within blocks / function closures:
Is there a way around this without having to move everything to the top-level / global scope?
Using the following code in TypeScript results in practically the same JavaScript that you appear to be aiming for...
namespace MY_NAMESPACE {
export class AssetService {
}
}
Resulting code:
var MY_NAMESPACE;
(function (MY_NAMESPACE) {
var AssetService = (function () {
function AssetService() {
}
return AssetService;
}());
MY_NAMESPACE.AssetService = AssetService;
})(MY_NAMESPACE || (MY_NAMESPACE = {}));
If you want to really reduce the scope, switch to external modules (AKA "modules" these days).
If you don't export the class from the module/file, it won't be visible globally, i.e. there's no reason to enclose class definitions in function scopes.
More about modules in TS: https://www.typescriptlang.org/docs/handbook/modules.html

Scala - unbound wildcard exception (Play Framework 2.3 Template)

I am using Play Framework 2.3 I am using the scala template engine to create my views and Java elsewhere.
My model extends an abstract parameterised object like so... (pseudo code)
Abstract object:
public abstract class MyObject<T> {
// various bits
public class MyInnerObject {
// more stuff
}
}
Model object (singleton)
public class SomeModel extends MyObject<SomeBean> {
public static SomeModel getInstance() {
if (instance == null)
instance = new SomeModel();
return instance;
}
// more bits
}
I then pass the model to the view from another view helper:
#MyHelper(SomeModel.getInstance())
MyHelper scala view template:
#*******************************************
* My helper
*******************************************#
#(myObj: some.namespace.MyObject[_])
#import some.namespace.MyObject
#doSomething(myInnerObj: MyObject[_]#MyInnerObject) = {
#* do some stuff *#
}
#for(myInnerObj <- myObj.getInnerObjects()) {
#doSomething(myInnerObj)
}
However I get an error on the line #doSomething(myInnerObj: MyObject[_]#MyInnerObject) stating
unbound wildcard exception
I am not sure the correct Scala syntax to avoid this error I had naively assumed that I could use the _ to specify arbitrary tyope but it won't let me do this.
What is the correct syntax?
UPDATE 1
Changing the method definition to:
#doSomething[T](myInnerObj: MyObject[T]#MyInnerObject)
gives further errors:
no type parameters for method doSomething: (myInnerObj:[T]#MyInnerObject)play.twirl.api.HtmlFormat.Appendable exist so that it can be applied to arguments (myObj.MyInnerObject)
--- because ---
argument expression's type is not compatible with formal parameter type;
found : myObj.MyInnerObject
required: MyObject[?T]#MyInnerObject
It would seem that the Twirl templating engine does not support this syntax currently, although I'm not 100% sure.
I can solve the problem by removing the doSomething method completely...
#*******************************************
* My helper
*******************************************#
#(myObj: some.namespace.MyObject[_])
#import some.namespace.MyObject
#for(myInnerObj <- myObj.getInnerObjects()) {
<div>#myInnerObj.getSomeProperty()</div>
}
But I am bout 10% happy with the solution... It works at least but it feels very restricting that I cannot delegate to methods to help keep my code maintainable. By the look of the comments the problem seems to be a limitation in Twirl, not allowing type arguments for functions in views.
Note: I have accepted this answer as it removes the original problem of the exception however this is only because the solution I want doesn't exist... yet.

In Haxe (JS Target) is there a way to make static members available to another class as if it was its own?

I have this Haxe class that is growing quite large. It consists mostly of static methods & properties. (It's a module set to compile as JS target).
I would like to separate some of the complex static functions into another class.
Is there any way to mark it with a metatag / indicate the other class is an "extension" to the original class?
Something like #:native("OriginalClass") class OtherClass {...}
The goal is to avoid having to write the full variable access (ex: OriginalClass.LOG_QUEUE vs. LOG_QUEUE) or clutter the imports with each OriginalClass's static methods / properties used at the top of the OtherClass. Basically, something to make it aware that it "is" using the same members as the OriginalClass (whenever an 'undefined' one is found, at compile-time).
Example:
If OriginalClass has static var LOG_QUEUE:Array<String>; then OtherClass would be aware that any usage of LOG_QUEUE compiles to this JS code OriginalClass.LOG_QUEUE
Alright, got a solution after discussing with Dima Granetchi from the Haxe experts group on Slack.
Now, although this will still generate the OtherClass that makes use of the OriginalClass's static members, you can cut down on the quantity of import statements for most (if not all) of the module/class's static members by using the wildcard * symbol, like in this example:
// OriginalClass.hx
package somePackage;
class OriginalClass {
public static var LOG_QUEUE:Array<String>;
public static function main() {
LOG_QUEUE = [];
OtherClass.doSomething();
}
public static function doSomethingOriginal() {
LOG_QUEUE.push("World!");
}
}
// OtherClass.hx
import somePackage.OriginalClass.*; // <-- Demonstrating the WILDCARD (*) symbol
class OtherClass {
public static function doSomething() {
LOG_QUEUE.push("Hello"); //Resolved to OriginalClass.LOG_QUEUE
doSomethingOriginal(); //Resolved to OriginalClass.doSomethingOriginal()
}
}
Although this is a minimal example, it becomes more useful when you have a few different dozen static members used in your OtherClass.
Note
TypeDefs defined in the OriginalClass used inside the OtherClass doesn't seem to get recognized/resolved (may be due to missing public accessor, but I was unable to set it on my typedefs). You can always import those specific TypeDefs with individual import statements, like so:
//Somewhere at the top of OtherClass.hx...
import somePackage.OriginalClass.MyTypeDef;