docs-bug(MatInput): How to nest / wrap material form controls

[leon]

Documentation Feedback

I find myself getting stuck on this again and again, and I've been using angular and material since it's inception, so by now it should have stuck up there in the old noggin, but alas.

Today we have a basic tutorial on how to do a completely custom form field
https://material.angular.io/guide/creating-a-custom-form-field-control

but there is no tutorials examples of how to take an existing matInput mat-select or other form controls and wrap them into a component.
Usually we need to do this to DRY things up and not have to have the same error messages, options or reoccurring fields multiple times.

These are some tutorials / examples I would like to see

Custom component to wrap sub field names, validation and errors
I have an Address FormGroup which contains
street, zipcode, city
and a couple of mat-form-fields with labels, inputs, errors
I now want to wrap this into a <app-address-field formGroupName="customer.address" />

Custom mat-select with static list of values and validation
I have a Language select that is reused in multiple places
I now want to use it <app-lang-select formControlName="project.language" />

Custom input with some kind of dialog picker
A User picker, should display the user name when done, and an icon to the right much like a date picker.
but then in the dialog we have some custom logic to list all users, and the value that comes out of the picker should be the database id for the user.
<app-user-picker formControlName="client.salesPerson" />

The struggles

Since matInput already implements ControlValueAccessor it must be possible to just provide / delegate functionality down to that child, but how?

I have multiple implementations of the above, but all of them feel over complicated, or the dirty state isn't working because of something.

We need best practices for creating wrapped form controls and form groups :)

Please let me know if you need more context or examples, I have plenty

[yurakhomitsky]

@leon I would like to take a look at some examples, just out of curiosity

[mjamin]

Documentation should also provide an example how a wrapper component should be designed in a ChangeDetectionStrategy.OnPush context, since the error state is updated during ngDoCheck, which isn't called when a component that wraps mat-form-field uses OnPush and isn't marked for checking.

From what I understand, this solution only works if the input is either within the same view as the form, or if the change detection strategy is set to Default

[pedroestabruxelles]

Since matInput already implements ControlValueAccessor it must be possible to just provide / delegate functionality down to that child, but how?

Found myself with the same problem last week.
What I did:
On the wrapper component add an @input() that receives the FormControl (I guess similar logic would apply for formgroup)
So the component would look like this:

<app-lang-select [control]="form.get('project.language')" />

And on the template
<mat-select [formControl]="control">

This approach made my life so much easier, i was already going crazy with the unnecessary complexity my component had before. But i agree that we need some sort of directive that would remove the need to do this way.

[lionelgaillard]

I think I have the same problem:

Inside a <mat-form-field />, I have a custom component <app-companies-select /> which contains <mat-select matInput />.
but I still have the mat-form-field must contain a MatFormFieldControl error, because mat-form-field only checks for MatFormFieldControl in its direct children and not all descendants.

[leon]

Bumped into my own problem yet again...

I found this old talk which goes over the problem some what.
but I still feel a material specific guide would be a good idea.

https://youtu.be/CD_t3m2WMM8?t=1522

[SparrowVic]

Some working example if you need: https://stackoverflow.com/questions/75850069/how-to-wrap-custom-angular-material-control-into-own-component

[atakchidi]

This particular problem is the reason I can not recommend to use angular material for any large scale project.

Custom material control is ridiculously complex when you need to wrap well known element like input. Even if done right still dies not solve all the problems since you probably want another wrapper around whole form-field stuff.

I have examples where I implemented all of the mentioned solutions like custom control value accessor or just passing the control inside a wrapping component.

Nothing works as a complete solid experience that whole form in single place gives you.
With above solutions you can defeat the mat-errrors and relations between form-field and input.
But you will still loose relation with

so for instance submitting errored form will not highlight controls., because mat-form-fields are nit aware of dirtiness. You need some fancy custom error strategy or propagate the form state to each wrapping control yourself.

Controls and buttons are two main things require redesign to make material compatible in flexibility to any other design system solution out there in the market.
Clear guide is a bare minimum starting point here.

[vborza]

@atakchidi may I ask you what UI component library would you recommend instead of Angular material? Do you have an experience with something more flexible?