@Optional dependency in Angular

Usage of @Optional (optional dependency), for example when LoginComponent is used as dialog or standalone. import { Optional } from ‘@angular/core’;   constructor( @Optional() private dialogRef: MatDialogRef<LoginComponent>, ) { … } import { Optional } from ‘@angular/core’; constructor( @Optional() private dialogRef: MatDialogRef<LoginComponent>, ) { … }

Reactive Form: previous value

let form = this.fb.group({ ‘hotelLocation’:[null] });   form.get(’hotelLocation’).valueChanges.subscribe(v => {   // HERE !! let prevVal = this.form.value[’hotelLocation’]; });let form = this.fb.group({ ‘hotelLocation’:[null] }); form.get(‘hotelLocation’).valueChanges.subscribe(v => { // HERE !! let prevVal = this.form.value[‘hotelLocation’]; });

Required @Input

selector: ‘app-test[id]‘ Component({ selector: ‘app-test[id]’ // id is required now }); export class TestComponent { @Input() id:number; }Component({ selector: ‘app-test[id]’ // id is required now }); export class TestComponent { @Input() id:number; }

rx.js – chain requests when need response from BOTH

On the end i need response from BOTH requests, but need chain them, because second request need something from first response. import { switchMap, map } from ‘rxjs/operators’;   this.restService.getFile(id) .pipe( switchMap((file:File) => this.restService.renderMd(file.markdown_id) .pipe(map((markdown:any) => { return { file:file, markdow: markdown }; })) ) ).subscribe((result:any) => { // I have results for two requests Read more about rx.js – chain requests when need response from BOTH[…]

@HostBinding example

import { Component, HostBinding, Input, OnInit } from ‘@angular/core’;   @Component({ selector: ‘app-host’, template: `<p>host works!</p>`, styles: [`:host(.someClass){ color: red; }`] }) export class HostComponent implements OnInit {   @Input(’idVal’) @HostBinding(’id’) id:string = ‘defaultId’; @Input() @HostBinding(’class.someClass’) withClass:boolean = true;   constructor() { }   ngOnInit(): void { }   }import { Component, HostBinding, Input, OnInit Read more about @HostBinding example[…]

updateValueAndValidity();

updateValueAndValidity() works for control, but NOT for children ! form:FormGroup; constructor(private fb:FormBuilder) { }   initForm() { this.form = this.fb.group({ ‘files’:[”, [this.fv.bind(this)]] }); }   /** * my validator */ fv(fc:AbstractControl) { console.log(’validate’, fc); // … }   /** * func that need to revalidate ‘files’ field */ someFunc() { // … this.form.updateValueAndValidity(); // NOT Read more about updateValueAndValidity();[…]

rx.js – chain requests

I don’t need result from first request, but need their response for second request (`switchMap` will be working, too) import { mergeMap } from ‘rxjs/operators’;   this.http.get(’/request1’).pipe( mergeMap((resp1:any) => this.http.post(’/request2′, resp1) ) ).subscribe(res => { // I have result from second request only console.log(res); });import { mergeMap } from ‘rxjs/operators’; this.http.get(‘/request1’).pipe( mergeMap((resp1:any) => this.http.post(‘/request2’, resp1) Read more about rx.js – chain requests[…]