Question

我正在尝试获取当前用户的活动作业列表：

jobListRef$: Observable<Job[]>;
...
this.afAuth.authState.take(1).subscribe(data => {
  if (data && data.uid) {
    this.jobListRef$ = this.database.list<Job>('job-list', query => {
         return query.orderByChild("state").equalTo("active");
    })
    .snapshotChanges().map(jobs => {
         return jobs.map(job => {
              const $key = job.payload.key;
              const data = { $key, ...job.payload.val() };
              return data as Job;
         });
    })
    .filter(val =>
         val.map(job => {
              return (job.employer == data.uid || job.employee == data.uid);
         })
    );
  }
});

问题始于过滤。根据官方文档，其参数的正确部分应返回布尔值，因此就像我的情况一样。但它仍然会返回整个条目而不过滤它们。

Answer 1

您要返回Array.map来电的结果，请查看其返回值：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map

您可能希望使用map代替filter：

.snapshotChanges().map(...)
.map(val => val.map(job => {
   return (job.employer == data.uid || job.employee == data.uid);
}));

Answer 2

我相信您想要反转地图并过滤运算符。

map

（filter将一个数组转换为另一个数组，.map(jobs => { return jobs.map(job => { const $key = job.payload.key; const data = { $key, ...job.payload.val() }; return data as Job; }) .filter(job => job.employer === data.uid || job.employee === data.uid ) })以减少数组。

或者您可以将过滤器链接到执行类型转换的地图

var innerTag = document.querySelector('.form-control-tag-inner');
var innerInput = document.querySelector('#conv-dest');
var innerContent = document.createRange().createContextualFragment('<span  class="label label-default"><span class="text-">nick</span><span class="close close-tag" aria-hidden="true">×</span><input type="hidden" name="participants[nick]" value="nick"></span>');
innerTag.insertBefore(innerContent, innerInput);

// sample event, attached on newly added content
var innerCross = document.querySelector('.form-control-tag-inner .close');
innerCross.onclick = function(){
    console.log( 'click' );
    return false;
};

Answer 3

不确定理解整个问题，但可能是：

this.jobListRef$ = this.afAuth.authState
    .filter(data => !!data && !!data.uid)
    .take(1)
    .switchMap(data =>
        this.database.list<Job>('job-list', query => query.orderByChild("state").equalTo("active"))
            .snapshotChanges()
            .map(jobs =>
                jobs.map(job => {
                    const $key = job.payload.key;
                    const data = { $key, ...job.payload.val() };
                    return data as Job;
                })
            )
            .map((jobs: Job[]) =>
                jobs.filter(job => (job.employer == data.uid || job.employee == data.uid))
            )
    );

使用Rxjs过滤Observable

3 个答案: