Angular 7 个行为主体与 class 个客体

Question

我有以下class

export class filter {
    public PageRecords: number;
    public SearchText: string;
    public SortColumn: string = null;
    public SortDirection: string = null;
    public StartingPos: number;
}

以下行为主体

filterParam = new BehaviorSubject(new filter);

更新主题

this.filterParam.next(<filter>{StartingPos  : 1,PageRecords : 10 })

当我得到subject的值时

this.filterParam.value

它只有我更新的两个道具StartingPos和PageRecords。它失去了其他道具。

如何解决？

Answer 1

这是因为你没有直接传递一个过滤器对象class。您正在将一些动态 json 投射到过滤器对象，但仅具有这两个属性。

你可以这样做：

const filterParam = new filter();
filterParam.StartingPos = 1;
filterParam.PageRecords = 10;

this.filterParam.next(filterParam);

编辑： 我没有注意到您只想更新 BehaviorSubject 值中的两个值。正如@ritaj 在下面的评论中建议的那样，你可以像他建议的那样做：

this.filterParam.next(Object.assign(this.filterParam.value, {StartingPos: 1, PageRecords: 10 }

Object.assign() copies the values (of all enumerable own properties) from one or more source objects to a target object. It has a signature of Object.assign(target, ...sources). The target object is the first parameter and is also used as the return value. Object.assign() is useful for merging objects or cloning them shallowly.

Answer 2

根据您的 class 参数名称的含义，我认为您想要一个 filter class 并且您只想在更改此过滤器时通知其他人。

我推荐这个代码：

filter = new filter;
filterParam = new BehaviorSubject<filter>(this.filter);

// later change the filter like this
changeFilter() {
  this.filter.StartingPos = 1;
  this.filter.PageRecords = 10;
  this.filterParam.next(this.filter);
}

Angular 7 个行为主体与 class 个客体

Angular 7 behavior subject with class object

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