index.ts

public createTask(req: Request, res: Response): Observable<mongoose.Document> {
        const body = req.body
        const self = this

        const task = body.task
        const projectId = body.projectId
        const moduleId = body.moduleId
        const timeRequired = body.timeRequired

        return Observable.create(function(observer: Observer<mongoose.Document>) {
            if ((!task) || !(typeof task === 'string')) {
                observer.error('Task name is required.')
            } else if (!projectId) {
                observer.error('Project id is required.')
            } else if (!mongoose.Types.ObjectId.isValid(projectId)) {
                observer.error('Invalide Project id.')
            } else if (!moduleId) {
                observer.error('Module id is required.')
            } else if (!mongoose.Types.ObjectId.isValid(moduleId)) {
                observer.error('Invalide Module id.')
            } else if ((!timeRequired) || !(typeof timeRequired === 'number')) {
                observer.error('Time is required.')
            } else {
                // Check if project and module id is correct.
                console.log('zipping the query.')
                zip(project.projectExists(projectId), module.moduleExists(moduleId, projectId), (proj, mod) => {
                    if (!proj) {
                        observer.error('Invalide Project id.')
                    } else if (!mod) {
                        observer.error('Invalide Module id.')
                    } else {
                        return true
                    }
                }).subscribe({
                    next: (value) => {
                        // Save Work
                        const newTask = new self.taskModule({ task: task, projectId: projectId, moduleId: moduleId, requiredTime: timeRequired })
                        self.save(newTask).subscribe({
                            next: (value) => {
                                observer.next(value)
                                observer.complete()
                            },
                            error: (err) => observer.error(err)
                        })
                    },
                    error: (err) => observer.error(err)
                })
            }
        })
    }