Question

我想在另一个中使用来自订阅方法的值，但是它给了我undefined，因为它不是异步的。有没有一种方法可以将这些值一起使用？我想在下面的订阅方法中再次使用this.internships，但它变得未定义。谢谢你的帮助！

代码：

ngOnInit(): void {
        this._internshipAssignmentService.getInternshipAssignments()
          .subscribe(internships => { this.internships = internships; <---- value which gives an object
          this.internshipsHelper = internships; console.log(this.internships)},
            error => this.msgs.push({
              severity: 'error',
              summary: 'Error',
              detail: 'Er is een onverwachte fout opgetreden.'
            }));
        this.sub = this._route.params.subscribe(
          params => {
            let id = +params['id'];
            this._internshipAssignmentService.getAllFavorites()
              .subscribe(f => {
                this.favorites = f;
                this.favorite = this.getFavoritesFromIdStudent(1);
                console.log(this.internships); <----- value which gives undefined 
                this.getFavorites(this.favorite);
              });
          }
      );
    }

Answer 1

this.internships为undefined，因为这些调用是异步的，您可以获得更多信息here。

另请注意，您使用的是多次订阅，这不是一个好习惯，您应该使用switchMap map，pluck之类的ngOnInit(): void { this.sub = this._internshipAssignmentService.getInternshipAssignments().do((internships) => { this.internships = internships; // not needed if you just use it in next callbacks this.internshipsHelper = internships; console.log(this.internships) }).catch(error => { this.msgs.push({ severity: 'error', summary: 'Error', detail: 'Er is een onverwachte fout opgetreden.' }) }).switchMap(internships => this._route.params.pluck('id').switchMap(id => { return this._internshipAssignmentService.getAllFavorites().do(f => { this.favorites = f; this.favorite = this.getFavoritesFromIdStudent(1); this.getFavorites(this.favorite); }) })) .subscribe(); }等operators组合您的观察结果。

//    going line by line for explanation

    public static Integer[] sort(Integer[] array)
    {
        Arrays.sort(array);//first of all sort the numbers in increasing order
        final double median;
        /*
        now in sorted numbers median is the
        --- average of middle two values for even count of numbers; like for 10 numbers median is (4th item +5th item )/2
        --- middle value if there are odd count of numbers like for 11 items the median is the 6th item
         */
        if (array.length % 2 == 0)
            median = ((double)array[array.length/2-1]+ (double)array[array.length/2])/2;
        else
            median =  array [array.length/2];
        //now we have the median



//        here we have a Comparator for comparing any value during with the median value
        Comparator<Integer> compareToMedian= new Comparator<Integer>()
        {
            @Override
            public int compare(Integer o1, Integer o2)
            {
//                first we check the distance of two numbers from the median; that is the difference from the median
                double value = Math.abs(o1 - median) - Math.abs(o2 - median);
                if (value == 0)//if the difference is same then we compare the numbers
                    value = o1 - o2;
                return (int)value;//otherwise we return the difference
            }
        };

        Arrays.sort(array, compareToMedian);//sort the numbers with respect to median
        return array;
    }

Angular2不能在另一个订阅中使用订阅的值（可观察）

1 个答案: