With ng-repeat what you're doing is inverting control of the management of your ViewModel from your controller to the helper directives to compose behavior.

Not supporting this is a mistake in ng2. @mhevery, If anyone's interested, I wrote up a blog post following the suggested Pipe solution made by @mhevery: https://webcake.co/object-properties-in-angular-2s-ngfor/, Ran into this issue, and used the solution posted somewhere since the pipe by @mhevery seem to have the same downside as here So what ngFor is doing, this time around, is enforcing best practices currently discovered in Angular 1 today (of managing the ViewModel in the component (container/controller/smart component) before passing it to the ngFor directive). var item of myMap.values(); var i = index, var item of myMap.entries(); var i = index, var item of myMap.entries(); var i = index; var mykey=item[0]; var myvalue=item[1]. I would expect iterating throw a Map like this: and that's working (I'm seeing the list) except that I'm having an "ExpressionChangedAfterItHasBeenCheckedError" error. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Please file a new issue if you are encountering a similar or related problem. No comments. Is iterating with *ngFor supported for ES6 Maps, or more generally, on objects implementing [Symbol.iterator()] ? ecmascript-6, typescript Similarly to that, I solved Iterating throw the Object with *ngFor by binding the "Object" to the component: What do you guys think about this solution? as an 'any' type because type '{}' has no index signature". I need to iterate over a large object which is just typed as "object". You were describing unpredictable ordering of object keys , which is different case. angularfix. Have a question about this project? @obscur666 when using your Pipe I ran into: Expression 'entity.props | values in Component@140:26' has changed after it was checked. But it seems to me, now in 2017, just using Object.keys is actually easier: This actually runs just fine! Angular's decision is based on Reply to this email directly or view it on GitHub Shouldn't something for smooth migration be provided by the library? Already on GitHub? Sign in Does anybody have an idea what I am missing here? In older posts I had found solutions using a generator within a custom Symbol.iterator function to make the large object iterable with a for..of loop. You're meant to refactor the behavior into a new directive for complex views such as a grid. With Angular 1, I would say no one took the time to take the next step of refactoring their behavior into components. @obscur666 thank you. @mhevery the thing is, reading through other tickets this does not seem to be a bug. They should rather But yes, in the strictest sense the pipe should make sure that it returns the same array. Well occasionally send you account related emails. P.S. Read more about our automatic conversation locking policy. @gdi2290 I experience the same thing, it renders them but then they're gone. It's a very often case when you don't care about order, you just need indexes of object for direct access (to display value in "View" mode, such as {{someList[someModel.id]}}), and to show options for select, . I'm not sure why the side-effect above happens with JIT. How do I call 2 API in parallel and the third right after that in RXJS. Or what is the current best practice to do such an iteration with ES2015 and TypeScript (2.2.2)? @jhiemer if it is a bug, then it should be filed, and fixed, rather than worked around it. At the minimum, I'd expect a default pipe to be available. They should rather adjust the Javascript specification so Browsers officially aren't allowed to change the order theoretically anymore. This seems like a huge glitch. @e-cloud The output of map.keys() is not an Array, it's an Iterator. ngFor doesn't support Object but ng-repeat does. As it was already said, the original question was about ES6 Map, which is ordered by its specification. How to fix Angular issue: Cannot read properties of null (reading 'cannotContainSpace'). Whenever you mutate the component, change the value of one of it's properties, then angular's change detection will be able to detect the changes in the component tree. But it's hacky. Note: Only a member of this blog may post a comment. Just checking if the mapToIterable pipe has been added to ng2? #6392. which is it makes it read only. And @dlinx just means that there is no need to use a pipe, it's supported by default with proper JavaScript code. You signed in with another tab or window. This Answer collected from stackoverflow and tested by AngularFix community admins, is licensed under. this can be better supported by a pipe which converts an object into array The standard uses a list type to describe it; adding a new element appends it to the end of the list of the key-value pairs, and changing the value of an element leaves the order intact. http://stackoverflow.com/questions/34313743/expressionchangedafterithasbeencheckedexception-since-angular-2-beta. This example doesn't work with JitChangeDetection with changeDetection: ON_PUSH but the default one is fine. to your account. Libraries and developer are used to work with objects Please let me know and I will gladly do it https://help.github.com/articles/creating-a-pull-request/, @mhevery @IsaacBorrero - here is what I am using - https://gist.github.com/amcdnl/202596c5b85cc66d7002d10bde3ab514. Only arrays and iterables are allowed in Angular-11 Application, Why is @angular/core/core has no exported member 'FactoryDeclaration'. theory, but the practice tells us something different. Successfully merging a pull request may close this issue. ;). Are there more solid approaches? For what it's worth, as opposed to the order of properties in an object, the order of the elements of a Map has been strictly defined from the first version of ECMAScript which introduced it. @mhevery I apologize, but what does that mean? Normally I would tend to return a new array instead of changing the keys in the existing object. privacy statement. If so it is the design, I think that a solution for the migration also should be in the design. I have trouble about a migration from ng-repeat to ngFor. What's going on is that ngFor is enforcing the developer to shape the collection correctly. Oddly enough, the original example works in changeDetection: ON_PUSH and JitChangeDetection until ChangeDetection does another tick then it removes them. Or that looping at all is problematic? Some developers even go so far as to say if Angular 1 did not include ng-repeat then we wouldn't have any performance problems since developers would have to consider how to manage their collections in a view. my code seems not working. But that's definitely a matter of taste. Is there an issue item that I can track to get status updates? @rolandjitsu this is kinda supported if you write it like this example, @mhevery inside of *ng-for this doesn't work var i = index; var mykey=item[0]; var value=item[1]. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map, https://webcake.co/object-properties-in-angular-2s-ngfor/, https://gist.github.com/amcdnl/202596c5b85cc66d7002d10bde3ab514, http://www.ecma-international.org/ecma-262/6.0/#sec-map.prototype.set, feat(core): @Volatile() decorator to allow unstable properties for change detection, ngFor with possibility of assign key value like ES6 feature, feat(core): KeyValueDiffer support for NgForOf, feat(common): new pipe to support object for ngFor, Child changed causes entire list to be recreated, Provide primitives to iterate ES6 Maps with ngFor. @mhevery What is "not assignable to parameter of type never" error in TypeScript? Can I already make use of a pipe inside ng-for that would transform that map into an array for instance? error thrown when using angular cdk virtual scroller, Property does not exist on type 'IntrinsicAttributes' with useFormContext and custom tag, TypeError: Cannot set properties of undefined (setting 'object'), Angular web components with custom elements error, How to convert date into this 'yyyy-MM-dd' format in angular 2, 100% working solution for TypeError: Cannot read properties of null (reading 'classList') React. If you want to learn more about ChangeDetection that's a post by Victor Savkin. On Sun, Dec 20, 2015 at 6:06 PM Marc J. Schmidt notifications@github.com Somehow I allways get the following Issue Code is: const foo = (foo: string) => { const result = [] result.push(foo) Issue with *ngFor, I cannot fetch the data from my component.ts to my component.html The Issue I installed CDK Virtual Scroller in my ionic 5.3.3 project: npm add @angular/cdk T Issue Recently I changed my custom input components to use react useFormContext instead o Issue I have a function that when calling it opens a modal from ngbModal, I have imported Issue I am trying to create a basic web component in Angular with Angular Elements. I am trying to iterate over Map values with the built in ng-for, but I can see that for some reason it is not working. adjust the Javascript specification so Browsers officially aren't allowed This was supported in ng1, but we think it was a mistake and will not be supported in NG2,
. It contains an unknown number of objects of the same type. Does the built in ng-for actually support iterating over maps? I wrote a pipe, objectToIterable, for this. In Angular 1 a lot of "perf" problems were due to developers overloading ng-repeat without considering what is really going on (leaky abstraction). In the specs, you can iterate over a Map iterable with: And none of the ES5 standard for ()/for ( in ) will work with that. @mhevery sounds fair enough. Why so complicate to iterate over map? While this may hurt migration a little bit, it forces developers down the correct path of managing their state correctly. By clicking Sign up for GitHub, you agree to our terms of service and #2246 (comment). This behaviour is described in different tickets/stackoverflow entries. How to iterate over keys of a generic object in TypeScript? that way (especially for configurations). Error trying to diff '[object Object]'. When I get an object and transform it into a array I need to return a new object, which results into the error. So fa Issue I want to convert current data into 'yyyy-MM-dd' format in .ts file Issue I am having this header which on scroll, I want to change the background to a differ Issue I want to make 2 API calls in Parallel and then the third immediately after that. Here I wrote the type object in let bigObject: BigObject. Other operations use the same list representation. I did it already, but it means we multiply *2 size of list in memory and had to use more lines of code. Angular's decision is based on theory, but the practice tells us something different. @mhevery that would help a lot. compiler blows up when it sees [. I would expect to bee faster than the pipe solution but that need to bee verifyed. It contains an unknown number of objects of the same type. Instead just used something that was suggested somewhere else, sorry can't find where. but that is known). Copyright var creditsyear = new Date();document.write(creditsyear.getFullYear()); browser sustain the key order of objects (except if you use numbers as key, If there are no other reasons than the perceived inconsistent ordering, considering that iterating through Maps would be very convenient, maybe another look at this could be justified? I think the current design is fine. and sorts the keys. 11:30 AM But the TypeScript compiler keeps giving me the error "error TS7017: Element implicitly h Misleading error message "Cannot find a differ supporting object '[object Object]'". You can use a better type. @mhevery @dlinx, ironically, what you've post just proves my thought. This action has been performed automatically by a bot. @mhevery Hi. Is it that ordering is inconsistent, in which case, does that matter? This issue has been automatically locked due to inactivity.

Issue I have created a custom ValidationFn in angular. to change the order theoretically anymore. wrote: Jupp, especially when you take into consideration that all current modern This whole tweaking really feels a bit buggy in Angular 2.

Jupp, especially when you take into consideration that all current modern browser sustain the key order of objects (except if you use numbers as key, but that is known). The problem is see is getting an object with properties and returning an array. @vsavkin is working on a less strong dev mode, which will treat this as OK. The problem with ng-repeat was that it allowed for both objects and map which allowed more developers to shoot themselves in the foot (more often when they are concerned with the order). See http://www.ecma-international.org/ecma-262/6.0/#sec-map.prototype.set for the Map.prototype.set() function. Or that has not been implemented yet? @IsaacBorrero It has not, would you like to make a PR? The text was updated successfully, but these errors were encountered: Maps have no orders in keys and hence they iteration is unpredictable. :I do not fully understand the internals of the change detection (like when the next tick occurs). Maybe with a generic interface BigObject for your dictionary? Libraries and developer are used to work with objects that way (especially for configurations). This change may also hurt prototyping which was one of Angular 1's strongest strength but someone could also create a ng-repeat/orderBy/filter directive/pipes which has the same API that relied on side effects, Maps iterate in order per https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map the output of map.keys() is an array. Keyspipe does't get its place. ;).