Angular2不能在另一个订阅中使用一个订阅的值(可观察)

本文介绍了Angular2不能在另一个订阅中使用一个订阅的值(可观察)的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我想在另一个方法中使用订阅方法中的值，但是它给我未定义的信息，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，但是它变得不确定.谢谢您的帮助！

I wanted to use a value from a subscribe method in another one, but it gives me undefined because it is not async. Is there a method to use those values together? I want to use this.internships another time in the following subscribe method but it becomes undefined. Thank you for helping!

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); }); } ); }

推荐答案

this.internships是undefined，因为这些调用是异步的，所以您可以获得更多信息此处.

this.internships is undefined because these calls are asynchronous, you can get more informations here.

还请注意，您正在使用多个订阅，这不是一个好习惯，您应该使用一些操作符(例如switchMap map，pluck等)

Also note that you are using multiple subscription, which is not a good practice, you should combine your observable using some operators like switchMap map,pluck, etc.

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(); }