I'm trying to 'port' some script to the Dart. To learn how everything work etc.
But there is a problem - in JavaScript we can set and get any variable in the object.
In Dart we have a Map class. And I have no idea how to use it (there is not so many help from Dart API Reference).
Currently I have:
Map settings;
//Then I get an dynamic result of a function that gives either null or object.
settings = result ?? {};
settings.someVar = 5;
And this code produces the following error:
"The setter 'someVar' is not defined for the class 'Map'."
Of course I can just 'invent' a new class Settings, but is there any other solutions?
With a Map, you get and put values with the [] and []= operators. So in this case you would use it like so;
settings['someVar'] = 5;
You can also use the addAll method;
settings.addAll({'someVar': 5, 'someOtherVar': 10});
Dart API References: operator [], operator []=, addAll
Related
I have a matcher that works perfectly for matching operator() calls on instances of a class or classes derived from that class. For example, it matches the final line of:
class MyBase { void operator()(...) {} };
MyBase b;
b(parameters);
using a matcher like:
const auto MyBaseExpr =
expr(hasType(cxxRecordDecl(isSameOrDerivedFrom("::MyBase"))));
Finder->addMatcher(traverse(
TK_AsIs, cxxOperatorCallExpr(
hasOverloadedOperatorName("()"),
hasArgument(0, anyOf(MyBaseExpr, MyOtherBaseExpr)),
hasAnyArgument(...),
this);
But I'd also like to be able to match such calls on instances of typedefs for the base or derived types like in the last line below:
typedef MyBase MyTypedef;
MyTypedef t;
t(parameters);
and I can't seem to fathom the correct way to specify this match. Attempting to use hasUnqualifiedDesugaredType rather than hasType doesn't work since it works on a type rather than a Decl and if I try to do more matching with the type then I can't use isSameOrDerived which returns a Matcher<CXXRecordDecl>. A similar problem occurs when trying to use hasCanonicalType:
.../RedundantStringCStrCheck.cpp:193:40: error: invalid initialization of reference of type ‘const clang::ast_matchers:
:internal::Matcher<clang::QualType>&’ from expression of type ‘clang::ast_matchers::internal::BindableMatcher<clang::Decl>’
193 | expr(hasCanonicalType(cxxRecordDecl(isSameOrDerivedFrom("::MyBase"))));
MyTypedef is defined from MyBase so its Canonical Type should be MyBase. More information about canonical type: https://clang.llvm.org/docs/InternalsManual.html#canonical-types
This is the example from LibASTMatchersReference , it uses hasType().
Thien Tran provided the pointer which led me to the right answer. Here's my original expression
const auto MyBaseExpr =
expr(hasType(cxxRecordDecl(isSameOrDerivedFrom("::MyBase"))));
I was trying to use:
const auto MyBaseExpr =
expr(hasCanonicalType(cxxRecordDecl(isSameOrDerivedFrom("::MyBase"))));
but the description of hasCanonicalType in LibASTMatchersReference shows that it takes and returns Matcher<QualType> yet cxxRecordDecl has type Matcher<Decl>, so this did not compile.
The mismatch of types can be corrected by inserting a call to hasDeclaration. It's then also necessary to keep the call to hasType in order to turn the Matcher<QualType> result of hasCanonicalType back into something that can be passed to expr.
After all that I ended up with:
const auto MyBaseExpr =
expr(hasType(hasCanonicalType(hasDeclaration(cxxRecordDecl(isSameOrDerivedFrom("::MyBase"))))));
which seems to work perfectly.
I am moving java script to dart, in java script I create dynamic variable like
window["text" + pageNumber] = 123;
alert(window["text" + pageNumber]);
How can I do it with dart?
In Dart Window (the type of window) is a class. You can't dynamically add properties to a Dart class.
window["text" + pageNumber] = 123; would work with a Map. Object representation in JS is quite similar to a map and therefore this works there.
If another class implements the [] operator you could call it on instances of that class as well but it would still not add properties. What it actually does just depends on the implementation of the [] operator.
There are probably different ways in Dart to achieve what you want, but you didn't add details about what actual problem you try to solve.
You can use normal global variables in Dart like explained in
Global Variables in Dart.
For your use case you can create a global Map variable this way
final Map<String,int> myGlobals = <String,int>{};
to create a map that stores integer values with string names.
Set values with myGlobals['someName'] = 123; and read them with print(myGlobals['someName']);.
If you need to set a global value that is also available for JS libraries you might use, you can use dart-js-interop
import 'dart:js';
import 'dart:html';
main() {
int pagenumber = 5;
context['Window']['text$pagenumber'] = 123;
window.alert('${context['Window']['text$pagenumber']}');
}
Try it on DartPad.
Hint:
"text" + pageNumber doesn't work when pageNumber is not a string.
In Dart you can't add string and numbers.
"text" + pageNumber.toString() would work but 'text$pagenumber' is a more darty way to do this. In string interpolation toString() is called automatically for you.
See also Dart js-interop not working if .dart file isn't included.
I wish to have the sub-classes of a super-class "registered" by an arbitrary name - whenever I declare a sub-class I wish to also have it entered into the super-class.sub Map.
Is there any way to accomplish this outside of main()?
// base class
class Mineral{
final String formula;
static Map<String,Mineral> sub = {}
Mineral( this.formula );
}
// sub class - declare and register
class Mica extends Mineral{
Mica( String formula ) : super( formula );
}
Mineral.sub['mica'] = Mica; // oops!
when I run this, I get
Error: line 10 pos 1: unexpected token 'Mineral' Mineral.sub['mica'] = Mica;
assuming that executable code is not allowed outside main().
cannot put within the super-class since other sub-classes may declared later, outside the library.
Dart has no way to run code as part of a library being loaded.
Executable code can only be put inside methods, or in field initializers, and static field initializers are lazy so they won't execute any code until you try to read them.
This is done to ensure quick startup - a Dart program doesn't have to execute any code before starting the main library's "main" method.
So, no, there is no way to initialize something that isn't constant before main is called.
Either
Mineral.sub['mica'] = new Mica();
or
static Map<String,Type> sub = {};
When you assign Mica you assign the Type Mica. new Mica() is an instance of Mica that is of the kind Mineral and can be assigned to the map you declared.
edit
Maybe you want to initialize the sub map:
static Map<String,Mineral> sub = {'mica': new Mica()};
hint: the semicolon is missing in this line in your question.
Say I have an instance of a class Foo, and I want to grab a list of all of its methods that are annotated a certain way. I want to have a reference to the method itself, so I'm not looking to use reflection to invoke the method each time, just to grab a reference to it the first time.
In other words, I want to do the reflection equivalent of this:
class Foo {
a() {print("a");}
}
void main() {
var f = new Foo();
var x = f.a; // Need reflective way of doing this
x(); // prints "a"
}
I have tried using InstanceMirror#getField, but methods are not considered fields so that didn't work. Any ideas?
As far as I understand reflection in Dart, there's no way to get the actual method as you wish to. (I'll very happily delete this answer if someone comes along and shows how to do that.)
The best I can come up with to ameliorate some of what you probably don't like about using reflection to invoke the method is this:
import 'dart:mirrors';
class Foo {
a() {print("a");}
}
void main() {
var f = new Foo();
final fMirror = reflect(f);
final aSym = new Symbol('a');
final x = () => fMirror.invoke(aSym, []);
x(); // prints "a"
}
Again, I know that's not quite what you're looking for, but I believe it's as close as you can get.
Side note: getField invokes the getter and returns the result -- it's actually fine if the getter is implemented as a method. It doesn't work for you here, but for a different reason than you thought.
What you're trying to get would be described as the "closurized" version of the method. That is, you want to get the method as a function, where the receiver is implicit in the function invocation. There isn't a way to get that from the mirror. You could get a methodMirror as
reflect(foo).type.methods[const Symbol("a")]
but you can't invoke the result.
I want to do this in Actionscript:
typeof(control1) != typeof(control2)
to test if two objects are of the same type. This would work just fine in C#, but in Actionscript it doesnt. In fact it returns 'object' for both typeof() expressions because thats the way Actionscript works.
I couldn't seem to find an alternative by looking in the debugger, or on pages that describe typeof() in Actionscript.
Is there a way to get the actual runtime type?
The best way is to use flash.utils.getQualifiedClassName(). Additionally, you can use flash.utils.describeType() to get an XML document the describes more about the class.
Actionscript 3 has an is operator which can be used to compare objects. Consider the following code:
var mySprite:Sprite = new Sprite();
var myMovie:MovieClip = new MovieClip();
trace(mySprite is Sprite);
trace(myMovie is MovieClip);
trace(mySprite is MovieClip);
trace(myMovie is Sprite);
Which will produce the following output:
true
true
false
false
This will work for built-in classes, and classes you create yourself. The actionscript 2 equivalent of the is operator is instanceof.
You'll want to use the Object.prototype.constructor.
From the documentation:
dynamic class A {}
trace(A.prototype.constructor); // [class A]
trace(A.prototype.constructor == A); // true
var myA:A = new A();
trace(myA.constructor == A); // true
(Conveniently, this is also how to check types in javascript, which is what originally led me to this in the docs)
So, to test this out before I posted here, I tried it in an app I have, in a class called Player. Since the prototype property is static, you can't call it using "this" but you can just skip the scope identifier and it works:
public function checkType():void {
trace(prototype.constructor, prototype.constructor == Player);
// shows [class Player] true
}
Is there a way to get the actual runtime type?
Yes.
var actualRuntimeType:Class = Object(yourInstance).constructor;
Some other answers already refer to .constructor, but you can't always directly access .constructor in ActionScript 3. It is only accessible on dynamic classes, which most classes are not. Attempting to use it on a regular class will cause a compile-time error under the default settings.
However, because every class inherits from Object, which is dynamic, we can look up their .constructor property just by casting an instance to Object.
Therefore if we are not interested in subclasses, we can confirm that two instances are of exactly the same class by simply evaluating this:
Object(instanceA).constructor === Object(instanceB).constructor;
I learned of this from the post "Get the class used to create an object instance in AS3" by Josh Tynjala.
A even simpler alternative that also works for me is just:
var actualRuntimeType:Class = yourInstance["constructor"];
The runtime is entirely capable of giving you the .constructor, it's just that the compiler complains if you use that syntax. Using ["constructor"] should produce the same bytecode, but the compiler isn't clever enough to stop you.
I included this second because it hasn't been tested anywhere except my current Flash environment, whereas several users have said that the method described above works for them.
If you want to account for inheritance, then you might want to try something like this:
if (objectA is objectB.constructor || objectB is objectA.constructor)
{
// ObjectA inherits from ObjectB or vice versa
}
More generally, if you want to test whether objectA is a subtype of objectB
import flash.utils.getDefinitionByName;
import flash.utils.getQualifiedClassName;
...
if (objectA is getDefinitionByName(getQualifiedClassName(objectB)))
{
...
}
Object obj = new Object();
Object o = new Object();
if(o.getClass().getName().endsWith(obj.getClass().getName())){
return true;
}else{
return false;
}