On the trail of this question by Codesections, I'm trying to add a phaser to a variable using traits. Something like this:
my &doing-good is Block will enter {
.add_phaser: "ENTER",
{
if Backtrace.new.grep: { .subname ~~ /bad/ } {
fail("Not authorized to call this");
}
}
};
This fails with is trait on &-sigil variable not yet implemented. Sorry.
I arrived to this because there seems no way to declare that as a block; by default is a Callable, and add_method does not work on Callables, apparently. Any other way of doing this?
Related
I'm fairly new to kotlin coroutines, and I have what I think is a somewhat esoteric use case related to how runBlocking and coroutine contexts interact.
To start with, a simple example. Let's say I've got a dead simple context element. Nothing fancy.
class ExampleContext(val s: String) : AbstractCoroutineContextElement(Key) {
companion object Key : CoroutineContext.Key<ExampleContext>
}
When I run these examples, they behave exactly the way I'd expect them to:
runBlocking(ExampleContext("foo")) {
println(coroutineContext[ExampleContext.Key]?.s) // prints "foo
}
runBlocking(ExampleContext("foo")) {
launch {
println(coroutineContext[ExampleContext.Key]?.s) // prints "foo"
}
}
runBlocking(ExampleContext("foo")) {
launch(ExampleContext("bar")) {
println(coroutineContext[ExampleContext.Key]?.s) // prints "bar"
}
}
When I do this it prints null (as I would expect it to, because it runBlocking defaults to having EmptyContext in its constructor):
runBlocking(ExampleContext("foo")) {
runBlocking {
println(coroutineContext[ExampleContext.Key]?.s) // prints null
}
}
So here's my conundrum. The docs (and all the guidance I've found on the web) basically say don't do this: runBlocking is supposed to be run at the outermost layer of the coroutine logic and that's it. No nesting. What I'm working on is a library that needs to populate some context for access inside code that I don't own that gets called later (basically, you can think of it like an interceptor). The rough pseudocode looks a little like this:
class MyLibrary(otherPeoplesLogic: OtherPeoplesBusinessLogic) {
fun <IN, OUT> execute(input: IN): OUT {
... do my library's thing, including adding in a custom context element ...
try {
return otherPeoplesLogic.execute(input)
} finally {
... do my library's cleanup ...
}
}
}
To support coroutines in OtherPeoplesBusinessLogic, all I'd really have to do is add runBlocking like this:
class MyLibrary(otherPeoplesLogic: OtherPeoplesBusinessLogic) {
fun <IN, OUT> execute(input: IN): OUT {
... do my library's thing ...
runBlocking(myCustomContext) {
try {
return otherPeoplesLogic.execute(input)
} finally {
... do my library's cleanup ...
}
}
}
}
So long as all OtherPeoplesBusinessLogic::execute does is launch/async/etc, everything is fine: myCustomContext will be accessible. What I'm worried about is what happens if OtherPeoplesBusinessLogic::execute (which I'm not in control of) misbehaves and does its own runBlocking call with no context argument passed at all: what I think will happen is that myCustomContext will just silently get dropped like the example above. Not good, because it needs to be accessible.
Phew. A lot of explanation. Thanks for bearing with me. :)
So my ultimate question here is this: is there anything I can do (outside of scolding the users of my library to not call runBlocking) to prevent an accidental nested runBlocking call from dropping my context? Or am I just out of luck here and should scrap the whole idea?
I am currently trying out Ktor. But it already fails on registering a onClickListener to the button.
I am just wondering because the onClick extends from String. If I click on the onClick the Code I get is this one:
var CommonAttributeGroupFacade.onClick : String
get() = attributeStringString.get(this, "onclick")
set(newValue) {attributeStringString.set(this, "onclick", newValue)}
So I think onClick has a getter and setter but not more. I installed location and FreeMarker so this is my route:
get<CharityRoute> {
val id = it.id
call.respondHtml {
body {
h1 { +"${it.id}" }
ul {
for (n in it.list) {
li { +"$n" }
}
}
button {
text("Run function")
onClick = "Hello"
}
}
}
}
Maybe someone has more experience with Ktor and especially with Kotlinx.
Problem
It depends which module you are working in.
On the server-side (JVM) you can not write Javascript-Code in Kotlin and assign it to a function like that.
To find a solution, I have to further know, what exactly it is you want to achieve.
Here are two of many possibilities, what you could do:
Solution 1
You can assign a javascript-code as string. You did just that by assigning the code "Hello".
Maybe you want to call a function, which was globally made available in the window object?
Solution 2
In client-side JS code, you can import kotlinx.html.js.onClickFunction and simply write
button{
onClickFunction = { println("clicked") }
}
to execute code written in Kotlin.
I'm about to choose what language to use for a new project: Perl5 or Perl6. 6 wins so far except that it is missing Moo's lazy attributes. The two implementations I found in modules are missing the key functionality. Hence, my attempt write my own implementation.
Role vs. Class
First problem I've got into is the content of attribute's .package for one declared in a role. Consider the followin:
role HOW1 {
method compose ( Mu $class ) {
note "HOW1.compose";
nextsame;
}
}
role HOW2 {
method compose ( Mu $class ) {
note "HOW2.compose";
nextsame;
}
}
multi trait_mod:<is> (Attribute:D $attr, :$mooish!) {
note "Attribute's package.HOW: ", $attr.package.HOW;
note '$*PACKAGE.HOW: ', $*PACKAGE.HOW;
$attr.package.HOW does HOW1;
$*PACKAGE.HOW does HOW2;
}
class Foo {
has $.bar is mooish;
}
role FooRole {
has $.baz is mooish;
}
The output of the script follows:
Attribute's package.HOW: Perl6::Metamodel::ClassHOW.new
$*PACKAGE.HOW: Perl6::Metamodel::ClassHOW.new
HOW2.compose
HOW1.compose
Attribute's package.HOW: Perl6::Metamodel::GenericHOW.new
$*PACKAGE.HOW: Perl6::Metamodel::ParametricRoleHOW.new
HOW2.compose
As it is clearly seen from the output, applying a role to a metaclass always works for classes and only works for $*PACKAGE.HOW with roles. Use of $*PACKAGE instead of .package could be considered a solution, but not the one I'd really like to use. (Though, if there is no better way...)
Accessor
I would like to provide lazy functionality for private attributes too. Yes, this will be availabe with self!bar syntax only, but this is a sacrifice I'm willing to make. 😉 The problem is that all the examples of custome-made accessor I found so far are using Attribute.set_value() method which is way too low-level. I'd like to have something like this:
role MooishHOW {
method compose ( Mu $class ) {
my $accessor = $class.^add_private_method( 'bar1',
method () is rw {
note self.WHO, ".bar1";
Proxy.new(
FETCH => -> $o {
$!bar1;
},
STORE => method ( $val ) {
note "Storing";
$!bar1 = $val;
}
);
}
);
callsame;
}
}
multi trait_mod:<is> (Attribute:D $attr, :$mooish!) {
$attr.package.HOW does MooishHOW unless $attr.package.HOW ~~ MooishHOW;
}
class Foo {
has $.bar is mooish;
has $!bar1 is mooish;
method to-bar1 {
note "bar1 val:",self!bar1;
}
}
my $inst = Foo.new;
$inst.to-bar1;
But $!bar1 notation doesn't compile because of the scope (MooishRole). Are there a trick I'm missing which would allow referencing a private attribute on self?
Tricky one
Perhaps it is possible to make an attribute to be a Proxy container? This would greatly simplify the overall logic of laziness implementation.
I have answered all my questions by finally achieving the target and released AttrX::Mooish module.
So far, the answer for the first question is: no. $*PACKAGE is currently the only way.
Second question: have no answer, but the final code has to rely on set_value() anyway.
The tricky one happened to be possible: set_value() does binding of an attribue to a container making it possible to bind to a Proxy object. No need to for sacrifices, private attributes can be accessed directly with lazyness working on them.
Thanks everybody, your answers let me work around some rough edges!
I'm using the buildSequence function in Kotlin. How do I end the iteration in the middle of the function? I'm looking for something similar to C#'s yield break statement.
My code looks something like the following. I'm stuck at the TODO.
fun foo(list:List<Number>): Sequence<Number> = buildSequence {
if (someCondition) {
// TODO: Bail out early with an empty sequence
// return doesn't seem to work....
}
list.forEach {
yield(someProcessing(it))
}
}
EDIT
Apparently, I misdiagnosed the source. The issue is not returning from the buildSequence function. The following works for me:
fun foo(list:List<Number>): Sequence<Number> = buildSequence {
return#buildSequence
list.forEach {
yield(someProcessing(it))
}
}
EDIT 2
The issue is that I put the return in a local helper function that validates data at multiple points in the buildSequence (Hence the helper function). Apparently I'm not able to return from buildSequence within the helper function. The error message was not terribly helpful...
Just use return#buildSequence, which is a labeled return from lambda, while an unlabeled return would mean 'return from the function foo'.
See also: Whats does “return#” mean?
Since Kotlin v 1.3.x preferred sequence syntax changed. (buildSequence is replaced by kotlin.sequences.sequence)
Updated "early return from generator" code snippet (includes try-catch and == null early return examples) for post 1.3.x Kotlin:
// gen# is just a subjective name i gave to the code block.
// could be `anything#` you want
// Use of named returns prevents "'return' is not allowed here" errors.
private fun getItems() = sequence<Item> gen# {
val cursor: Cursor?
try {
cursor = contentResolver.query(uri,*args)
} catch (e: SecurityException) {
Log.w(APP_NAME, "Permission is not granted.")
return#gen
}
if (cursor == null) {
Log.w(APP_NAME, "Query returned nothing.")
return#gen
}
// `.use` auto-closes Closeable. recommend.
// https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.io/use.html
cursor.use {
// iterate over cursor to step through the yielded records
while (cursor.moveToNext()) {
yield(Item.Factory.fromCursor(cursor))
}
}
}
(Thx for all the prior posts that helped me get on "named return" track.)
I dont think minInvocation or maxInvocation is equivalent to times() in Mockito. Is there?
Please see this questions: Major difference between: Mockito and JMockIt
which has not been answered yet by anyone.
Edit
I found the answer myself: Adding it here for others who need this answered:
The solution is to use DynamicPartialMocking and pass the object to the constructor of the Expectations or NonStrictExpectations and not call any function on that object.
Then in the Verifications section, call any function on the object for which you want to measure the number of invocations and set times = the value you want
new NonStrictExpectations(Foo.class, Bar.class, zooObj)
{
{
// don't call zooObj.method1() here
// Otherwise it will get stubbed out
}
};
new Verifications()
{
{
zooObj.method1(); times = N;
}
};
I found the answer myself: Adding it here for others who need this answered:
The solution is to use DynamicPartialMocking and pass the object to the constructor of the Expectations or NonStrictExpectations and not call any function on that object.
Then in the Verifications section, call any function on the object for which you want to measure the number of invocations and set times = the value you want
new NonStrictExpectations(Foo.class, Bar.class, zooObj)
{
{
// don't call zooObj.method1() here
// Otherwise it will get stubbed out
}
};
new Verifications()
{
{
zooObj.method1(); times = N;
}
};