RxJS distinctUntilChanged - 对象比较 [英] RxJS distinctUntilChanged - object comparison

问题描述

我有一个对象流，我需要比较当前对象是否与前一个对象不同，并且在这种情况下发出一个新值.我发现distinctUntilChanged 操作符应该完全符合我的要求，但出于某种原因，它从不发出除第一个值之外的值.如果我删除 distinctUntilChanged 值会正常发出.

I have a stream of objects and I need to compare if the current object is not the same as the previous and in this case emit a new value. I found distinctUntilChanged operator should do exactly what I want, but for some reason, it never emits value except the first one. If I remove distinctUntilChanged values are emitted normally.

我的代码:

export class SettingsPage {
    static get parameters() {
        return [[NavController], [UserProvider]];
    }

    constructor(nav, user) {
        this.nav = nav;
        this._user = user;

        this.typeChangeStream = new Subject();
        this.notifications = {};
    }

    ngOnInit() {

        this.typeChangeStream
            .map(x => {console.log('value on way to distinct', x); return x;})
            .distinctUntilChanged(x => JSON.stringify(x))
            .subscribe(settings => {
                console.log('typeChangeStream', settings);
                this._user.setNotificationSettings(settings);
            });
    }

    toggleType() {
        this.typeChangeStream.next({
            "sound": true,
            "vibrate": false,
            "badge": false,
            "types": {
                "newDeals": true,
                "nearDeals": true,
                "tematicDeals": false,
                "infoWarnings": false,
                "expireDeals": true
            }
        });
    }

    emitDifferent() {
        this.typeChangeStream.next({
            "sound": false,
            "vibrate": false,
            "badge": false,
            "types": {
                "newDeals": false,
                "nearDeals": false,
                "tematicDeals": false,
                "infoWarnings": false,
                "expireDeals": false
            }
        });
    }
}

推荐答案

我遇到了同样的问题，并通过使用 JSON.stringify 来比较对象来修复它:

I had the same problem, and fixed it with using JSON.stringify to compare the objects:

.distinctUntilChanged((a, b) => JSON.stringify(a) === JSON.stringify(b))

肮脏但有效的代码.

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