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Improve type checking to include checking model binding #16952
Description
import {Component} from "@angular/core";
import {CommonService} from "../service/common.service";
@component({
selector: 'testb',
template: '<button (click)="aa()">输出 <button (click)="bb()">切换' +',
' <input [(ngModel)]="myh.n" #item (change)="cc(item.value)"/>
})
export class TestB {constructor(private commonService: CommonService) { } private mynumber: number; private myh: myObjct = new myObjct(3); aa() { console.log(this.commonService.hello) } bb() { this.commonService.hello = "test b hello" } cc(v: number) { this.myh.n =v console.log(this.myh) console.log( this.myh.n) console.log(JSON.stringify(this.myh)) }}
class myObjct{
private _n:numberconstructor(n: number) { this._n = n; } get n(): number { return this._n; } set n(value: number) { this._n = +value; }}
i must use +value to make my type to be number .or it will be string.
Reacted by Alexander Turtsevich, Valeriy Katkov, Eloi Simard-Quesnel and AugustZellmer
Activity
trotyl commentedon May 23, 2017
[()]syntax is just a syntax sugar of property binding and event binding. The generalized problem here is that Angular does not provide type checking for event bindings, nothing special tongModelChange.You should fill the issue template as a feature request, as it's expected at design level, rather than being a BUG. But this may not be possible for current mechanism, as it's just string comparison for event names, the source of the event is not being tracked during compilation.
100cm commentedon May 24, 2017
i think when angular 2 set a property of object , its will not check the type, how to check this ?
trotyl commentedon May 24, 2017
In the binding
(ngModelChange)="myh.n = $event",myh.nis the property you want to bind to, it's typed properly, but$eventis always declared asany.Theoretically the type of
$eventmay be determined by the generic type ofEventEmitter, but there may still be other conditions, like native DOM events and events provided by otherEVENT_MANAGER_PLUGINS.What's more for
ngModelChangeis that, there is no generic type used in theEventEmitter(in ng_model.ts), the expected declared type it's determined by theNG_VALUE_ACCESSOR, not theNgModel.So that's why I think this request is way to hard to implement this. Still, this is just my point of view.
[-]BUG:angular2 model bind make typescript type check missed[/-][+]Improve type checking to include checking model binding[/+]trotyl commentedon Jul 12, 2017
Possibly relates to #17483
angular-robot commentedon Jun 4, 2021
Just a heads up that we kicked off a community voting process for your feature request. There are 20 days until the voting process ends.
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angular-robot commentedon Jun 25, 2021
Thank you for submitting your feature request! Looks like during the polling process it didn't collect a sufficient number of votes to move to the next stage.
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alxhub commentedon Jul 8, 2021
I'm going to close this as resolved, actually.
In Ivy under
strictTemplates, the type of$eventis correctly determined by the generic type ofEventEmitterof the output in question. However, #13721 will likely need to be resolved as well, to truly solve the problem described in this issue.angular-automatic-lock-bot commentedon Aug 8, 2021
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