Trying to get the meaning of Uniswap v3-core, I rammed into an unexpected Solidity syntax which I cannot comprehend, so I need someone who could explain it.
the thing is about UniswapV3Pool.sol contract which can be found at both
etherscan.io and github of the project.
More to the point, there are the following lines:
406 flippedLower = ticks.update(
407 tickLower,
408 tick,
409 liquidityDelta,
410 _feeGrowthGlobal0X128,
411 _feeGrowthGlobal1X128,
412 secondsPerLiquidityCumulativeX128,
413 tickCumulative,
414 time,
415 false,
416 maxLiquidityPerTick
417 );
but the ticks variable is just a mapping:
93 mapping(int24 => Tick.Info) public override ticks;
So I do not get it. What update is called there?
There are some similar puzzling things, such as
386 position = positions.get(owner, tickLower, tickUpper);
where
97 mapping(bytes32 => Position.Info) public override positions;
There is no get on a mapping as well. What is going on?
UniswapV3Pool.sol extends a specific mapping type by functions defined in the Tick library:
using Tick for mapping(int24 => Tick.Info);
The Tick library then defines the update() function (GitHub source).
Same goes with the positions mapping extended by the Position library (GitHub source), as well as few others.
using Position for mapping(bytes32 => Position.Info);
Here's the Solidity docs for using ... for: https://docs.soliditylang.org/en/v0.8.11/contracts.html#using-for
Related
I'm using Supertest to test my APIs in my NestJS application. My tests seem to be working fine except for my DELETE request test, which throws this error:
ERROR [ExceptionsHandler] Converting circular structure to JSON
--> starting at object with constructor 'Socket'
| property '_writableState' -> object with constructor 'WritableState'
| property 'afterWriteTickInfo' -> object with constructor 'Object'
--- property 'stream' closes the circle
TypeError: Converting circular structure to JSON
--> starting at object with constructor 'Socket'
| property '_writableState' -> object with constructor 'WritableState'
| property 'afterWriteTickInfo' -> object with constructor 'Object'
--- property 'stream' closes the circle
at JSON.stringify (<anonymous>)
Here is the test I currently have:
it('should delete the relevant summary', (done) => {
request(app.getHttpServer())
.delete(`/engine/summaries/${summary_id}`)
.set('Authorization', `Bearer ${token}`)
.expect(204)
.end(done)
});
I initially thought it was because I didn't use the end() callback with 'done' passed into it, but that doesn't seem to be the issue. This is my return statement in my API if it helps: return res.status(204).send();
I've encountered this error before but it was because I was testing my asynchronous code incorrectly. However, this doesn't seem to be the issue here (or maybe it is?) and I've already spent the entire day trying to figure it out. Any help is greatly appreciated!
I totally missed the ES6 revolution and I'm returning to JavaScript after 7 years, to find a host of very strange things happening.
One in particular is the way Function.prototype.bind() handles class constructors.
Consider this:
// an ES6 class
class class1 {
constructor (p) {
this.property = p;
}
}
var class2 = class1.bind(passer_by);
var class3 = class2.bind(passer_by,3);
class2() // exception, calling a constructor like a function
class3() // idem
console.log (new class1(1)) // class1 {property: 1}
console.log (new class2(2)) // class1 {property: 2}
console.log (new class3() ) // class1 {property: 3}
// An ES5-style pseudo-class
function pseudoclass1 (p) {
this.property = p;
}
var property = 0;
var passer_by = { huh:"???" }
var pseudoclass2 = pseudoclass1.bind(passer_by);
var pseudoclass3 = pseudoclass1.bind(passer_by,3);
pseudoclass1(1); console.log (property) // 1 (this references window)
pseudoclass2(2); console.log (passer_by) // Object { huh: "???", property: 2 }
pseudoclass3() ; console.log (passer_by) // Object { huh: "???", property: 3 }
console.log (new pseudoclass1(1)) // pseudoclass1 {property: 1}
console.log (new pseudoclass2(2)) // pseudoclass1 {property: 2}
console.log (new pseudoclass3() ) // pseudoclass1 {property: 3}
Apparently class2 and class3 are identified as constructors, and class3 is a partial application of class1 that can generate instances with a fixed value of the first parameter.
On the other hand, though they can still act as (poor man's) constructors, the ES5-style functions are indeed served the value of this set by bind(), as can be seen when they act on the hapless passer_by instead of clobbering global variables as does the unbound pseudoclass1.
Obviously, all these constructors somehow access a value of this that allows them to construct an object. And yet their this are supposedly bound to another object.
So I guess there must be some mechanism at work to feed the proper this to a constructor instead of whatever parameter was passed to bind().
Now my problem is, I can find bits of lore about it here and there, even some code apparently from some version of Chrome's V8 (where the function bind() itself seems to do something special about constructors), or a discussion about a cryptic FNop function inserted in the prototype chain, and, if I may add, the occasional piece of cargo cult bu[beep]it.
But what I can't find is an explanation about what is actually going on here, a rationale as to why such a mechanism has been implemented (I mean, with the new spread operator and destructuring and whatnot, wouldn't it be possible to produce the same result (applying some arguments to a constructor) without having to put a moderately documented hack into bind()?), and its scope (it works for constructors, but are there other sorts of functions that are being fed something else than the value passed to bind() ?)
I tried to read both the 2015 and 2022 ECMA 262 specifications, but had to stop when my brains started leaking out of my ears. I traced back the call stack as:
19.2.3.2
9.4.1.3
9.4.1.2
7.3.13
where something is said about constructors, in a way: "If newTarget is not passed, this operation is equivalent to: new F(...argumentsList)". Aha. So this pseudo-recursive call should allow to emulate a new somehow... Erf...
I'd be grateful if some kind and savvy soul could give me a better idea of what is going on, show me which part(s) of the ECMA specs deal with this mechanism, or more generally point me in the right direction.
I'm tired of banging my head against a wall, truth be told. This bit of Chrome code that seems to indicate bind() is doing something special for constructors is just incomprehensible for me. So I would at least like an explanation about it, if everything else fails.
This doesn't have anything to do with classes specifically but with how .bind works.
You have been on the right track. The most relevan section here is 9.4.1.2.
Just as a recap: ECMAScript distinguishes between two types of functions: callable functions and constructable functions. Function expressions/declarations are both, whereas e.g. class constructors are only constructable and arrow functions are only callable.
In the specification this is represented by function's internal [[Call]] and [[Construct]] methods.
new will trigger the invocation of the internal [[Construct]] method.
.bind will return a new function object with different implementations for [[Call]] and [[Construct]]. So what does the "bound" version of [[Construct]] look like?
9.4.1.2 [[Construct]] ( argumentsList, newTarget )
When the [[Construct]] internal method of a bound function exotic object, F that was created using the bind function is called with a list of arguments argumentsList and newTarget, the following steps are taken:
Let target be F.[[BoundTargetFunction]].
Assert: IsConstructor(target) is true.
Let boundArgs be F.[[BoundArguments]].
Let args be a new list containing the same values as the list boundArgs in the same order followed by the same values as the list argumentsList in the same order.
If SameValue(F, newTarget) is true, set newTarget to target.
Return ? Construct(target, args, newTarget).
What this means is that the bound constructor will "construct" the original function (F.[[BoundTargetFunction]]) with the bound arguments (F.[[BoundArguments]]) and the passed in arguments (argumentsList), but it completely ignores the bound this value (which would be F.[[BoundThis]]).
but are there other sorts of functions that are being fed something else than the value passed to bind() ?
Yes, arrow functions. Arrow functions do not have their own this binding (the value from the closest this providing environment is used instead), so bound arrow functions also ignore the bound this value.
I am trying to learn react redux api call
so I took an example and implemented in stackblitz but I am getting the below error when I select some channel and hit top news button
can you tell me how to fix it
providing my code and stackblitz below
https://medium.com/#lavitr01051977/basic-react-redux-app-with-async-call-to-api-e478e6e0c48b
https://stackblitz.com/edit/react-redux-realworld-j95tpu?file=actions/index.js
code
export function fetchPosts(channel) {
return function (dispatch) {
dispatch(requestPosts());
return fetch(`https://newsapi.org/v1/articles?source=${channel}&apiKey=${MY_API_KEY}`)
.then(response => response.json(),
error => console.log('An error occurred.', error),
)
.then((json) => {
dispatch(receivedPosts(json));
}, );
};
}
error
VM1672:37 Warning: React.createElement: type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it's defined in. Check the render method of `TopNews`.
in TopNews (created by Connect(TopNews))
in Connect(TopNews) (created by App)
in div (created by App)
in App
in Provider
Uncaught (in promise) Error: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it's defined in. Check the render method of `TopNews`.
at invariant (invariant.js:42)
at instantiateReactComponent (instantiateReactComponent.js:74)
at instantiateChild (ReactChildReconciler.js:44)
at eval (ReactChildReconciler.js:71)
at traverseAllChildrenImpl (traverseAllChildren.js:77)
at traverseAllChildren (traverseAllChildren.js:172)
at Object.instantiateChildren (ReactChildReconciler.js:70)
at ReactDOMComponent._reconcilerInstantiateChildren (ReactMultiChild.js:185)
at ReactDOMComponent.mountChildren (ReactMultiChild.js:224)
at ReactDOMComponent._createInitialChildren (ReactDOMComponent.js:703)
The actual problem is an import/export syntax issue. I'll walk you through how to find it.
The problem's real location is shown by the component stack trace:
Warning: React.createElement: type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it's defined in. Check the render method of `TopNews`.
in TopNews (created by Connect(TopNews))
in Connect(TopNews) (created by App)
in div (created by App)
in App
in Provider
If we look in TopNews.js, it only renders <h3>, <div>, and <NewsItem>. h3 and div are just basic tags, so it's probably NewsItem that's the problem.
At the top of TopNews.js, you have:
import { NewsItem } from '../components/NewsItem';
However, in NewsItem.js, you have:
export default NewsItem ;
So, you're doing a default export, but a named import, and so NewsItem is undefined in TopNews.js.
Try changing it to be import NewsItem from "../components/NewsItem" and it should work.
I am using Plugin.Geofence i Implemented its interface,Installed its dependencies i.e. .NETStandard 2.0 and Xamarin.GooglePlayServices.Location.
I am getting this exceptions System.InvalidCastException: Specified cast is not valid. when i run StartMonitoring method.
I am calling this method in the App() Constructor.
public App ()
{
InitializeComponent();
MainPage = new NavigationPage(new MainPage());
CrossGeofence.Current.StartMonitoring(new GeofenceCircularRegion("MyRegion", 31.475085, 74.305833, 200)
{
//To get notified if user stays in region for at least 5 minutes
NotifyOnStay = true,
StayedInThresholdDuration = TimeSpan.FromMinutes(5)
});
}
Tried everything but couldn't resolve this
For anyone looking for a solution to this, ensure that before calling "CrossGeofence.Current" that the correct permissions have been requested and granted. If not, you'll see this error.
I have a very specific question, and i really searched the answer all over the place...
Here is a situation: i have a Scatter-Gather component with a custom aggregation strategy.
http://clip2net.com/s/j66jK8 - Image of a subflow
Semantic of this process is rather simple. Request comes with Basic Authentication Header, the upper road calls just empty java processor, which returns original payload, the lower road authenticates user over LDAP, and returns Boolean result of this authentication process. Custom aggregation class checks result and if authentication was OK, then returns original payload, which results from the road #1. If not OK, then throws exception. Nothing wrong here, it works.
There is a bit tricky thing. If a user passed wrong authentication data then exception occurs in ldap:bind module. According to documentation exception is propagated to the Scatter-Gather so i'm trying to catch it using this:
#Override
public MuleEvent aggregate(AggregationContext context) throws MuleException {
for (MuleEvent event: context.collectEventsWithExceptions()) {
event.getMessage().getExceptionPayload().getException().printStackTrace();
throw new RuntimeException(event.getMessage().getExceptionPayload().getException());
}
MuleEvent result = DefaultMuleEvent.copy(context.getEvents().get(0));
if (!(Boolean) context.getEvents().get(1).getMessage().getPayload()) {
throw new SecurityException();
}
return result;
}
BUT!
As a result i see exception which stacktrace does not have javax.naming.AuthenticationException which was rased by ldap:bind component, and was printed to log automaticaly (see below).
So, my question is: how can i reach and rethrow this javax.naming.AuthenticationException exception out of Custom Aggregation Class?
I'd appreciate all you ideas and help. Thank you in advance.
WARN 2014-10-15 20:51:18,552 [[minkult].ScatterGatherWorkManager.02] org.mule.module.ldap.api.jndi.LDAPJNDIConnection: Bind failed.
ERROR 2014-10-15 20:51:18,559 [[minkult].ScatterGatherWorkManager.02] org.mule.retry.notifiers.ConnectNotifier: Failed to connect/reconnect: Work Descriptor. Root Exception was: javax.naming.AuthenticationException: [LDAP: error code 49 - INVALID_CREDENTIALS: Bind failed: Attempt to lookup non-existant entry: cn=sim,ou=people,dc=example,dc=com]; resolved object com.sun.jndi.ldap.LdapCtx#5de37d66. Type: class javax.naming.AuthenticationException
COUNT: 1
org.mule.api.transport.DispatchException: route number 1 failed to be executed. Failed to route event via endpoint: InterceptingChainLifecycleWrapper 'wrapper for processor chain 'null''
[
ScriptComponent{CheckAuth.component.553657235},
org.mule.module.ldap.processors.BindMessageProcessor#647af13d,
org.mule.module.ldap.processors.SearchMessageProcessor#2aac6fa7,
InvokerMessageProcessor [name=ldapUtils, object=com.at.mkrf.aggregate.LDAPUtils#5714c7da, methodName=findGroupByName, argExpressions=[#[payload], #[systemName]], argTypes=[Ljava.lang.Class;#5af349a6]
]. Message payload is of type: NullPayload
On a CompositeRoutingException, you can call:
exception.getExceptions().values()
to get an Array of Throwables thrown from within the scatter-gather. Then just re-throw the appropriate exception.