Angular2(RxJS) Subscription don't fire at first click

Question

I would like to observe the event inside of one componenet and then fire diffrent event i another one. I have declare service and such code inside

    private updateIncomingMaterial = new Subject<IncomingMaterial>();

    incomingMaterialUpdate$ = this.updateIncomingMaterial.asObservable();

   updateIncMaterial(incomingMaterialToUpdate: IncomingMaterial) {
       this.updateIncomingMaterial.next(incomingMaterialToUpdate);
   }

There is how i fire event in one component

    update(model: IncomingMaterial) {
    this.incMatService.updateIncMaterial(model);
    this.isEditorVisible = true;
    this.isUpdateMode = true;
}

and here how i want to subscribe it in another one

    ngAfterViewInit() {
    this.subscription = this.incMatService.incomingMaterialUpdate$.subscribe((model: IncomingMaterial) => {
        this.isUpdateMode = true;
        this.imForm.setValue(model);
    });
}

I dont know why it never go inside of subscription in the fist time when i click update button(inside i mean this.UpdateMode = true and this.imForm.setValue(model)).