我目前是Angular的新手。

异步管道的主要目标之一是自动为您处理订阅和取消订阅。

1.当处理删除或更新（两者都是API服务）时，我是否需要通过ngOnDestroy取消订阅？

projects$: Observable<Project[]>;

constructor(
    private projectService: ProjectService,
) { }

ngOnInit() {
    this.loadProject();
}   


loadProject(){
    this.projects$ = this.projectService.getProjects()
    .pipe(
        map(result => {
            if(result.success){
                return result.data;
            }
        })
    );
}


deleteProject(){
    if(this.projectToDelete){
        const id = this.projectToDelete.id;
        this.projectService.deleteProject(id).subscribe(result => {
            if(result.success){
                this.loadProject();
            }
        });
    }
}

是否有另一种方法可以从可观察中删除特定元素，而无需再次调用刷新项目$的api？类似于这样，而不是上面的：

//In this case this.projects type is not an Observable.
deleteProject(){
    if(this.projectToDelete){
        const id = this.projectToDelete.id;
        this.projectService.deleteProject(id)
        .subscribe(result => {
            if(result.success){
                this.projects = this.projects.filter(item => {
                    return item.id != id;
                });
                this.projectToDelete = null;
                this.closeModal();
            }
        });
    }
}