Question

我有一个数据结构，通过redux选择器我有studentIds = [123,124] 我还在我的redux商店中有学生实体对象，其中包含123和124的对象详细信息我想订阅[学生实体123，学生实体124]的数组。

我试过以下。但我有两个问题 1.减少后，不会打印任何值 2.我需要在步骤-2之后重置减少

  this.store
  .select(FilterSelector.getSelectedStudents)
  // Step - 1 Here we get an observable stream which has value of [123, 124]

  .switchMap(studentIds => {
    return from(studentIds);
  })
  // Step - 2 Here student-id 123 and 124 are streamed independently. the purpose is I can lookup student ids independently for the next step

  .mergeMap(studentId => {
    return this.store.select(StudentSelector.getStudentById(studentId));
  })
  // Step - 3 Here the student-id = 123 object and student-id = 124 object are streamed independently

  .pipe(
    reduce((acc, curr: Student) => {
      acc.push(curr);
      return acc;
    }, [])
   // Step - 4 Here the student-id = 123 object and student-id = 124 object are combined together and streamed as 1 single array

  )
  .subscribe(d => console.log(d));
  // I am expecting the array of student objects

Answer 1

您可以使用其他策略将两个实体放在一起

this.store.select(FilterSelector.getSelectedStudents)
.flatMap((ids:Array<number>)=>merge(ids.map(studentId=>this.store.select(StudentSelector.getStudentById(studentId)))))
    .subscribe((data)=>{...})

可观察的查找和聚合

1 个答案: