What is the best way to persist form state in an Angular Lazy Loading Module?

Question

What is the best way to persist form state in an Angular Lazy Loading Module?

I've set up 2 routes in my Angular 7 application,

{
    path: 'create',
    component: CreateComponent
},
{
    path: 'view',
    component: ViewComponent
}

Both of these routes are lazily loaded. The CreateComponent contains a form with several form fields, and the same goes for the ViewComponent.

The issue I'm facing is that when I navigate from the /create route or CreateComponent to the /view route or ViewComponent, all the form fields within the previous component (i.e. ViewComponent) get reset to their initial state (confirmed by returning to the /create route). This means that the form fields are automatically reset by Angular. The same problem occurs if I switch from the /view route to the /create route, causing all form fields in /view to be reset automatically.

How can I resolve this issue? I want the form fields to retain their previous values (even if the form hasn't been submitted yet) when navigating to other routes.

Thank you.

javascript angular typescript lazy-loading

Answer 1

Answer №1

One important thing to consider is that when you navigate away, an angular component gets destroyed and then recreated when you come back. There are various methods to preserve component data.

Utilize services to store the data and reuse it when the component is initialized once again.
Save data in local storage and reuse it upon component initialization.
RouteReuseStrategy. This offers a way to recycle angular components. Keep in mind that this might not work with sibling router outlets. Personally, I had difficulties making it functional for sibling routes. You can check out my previous response on implementing RouteReUseStrategy

Answer 2

One important thing to consider is that when you navigate away, an angular component gets destroyed and then recreated when you come back. There are various methods to preserve component data.

Utilize services to store the data and reuse it when the component is initialized once again.
Save data in local storage and reuse it upon component initialization.
RouteReuseStrategy. This offers a way to recycle angular components. Keep in mind that this might not work with sibling router outlets. Personally, I had difficulties making it functional for sibling routes. You can check out my previous response on implementing RouteReUseStrategy

Answer 3

Answer №2

Lazy loading is not the issue at hand here, for example, if you are utilizing reactive controls in your form,

userForm: FormGroup
constructor (private fb: FormBuilder) {}
ngOnInIt() {
 this.userForm = this.fb.group({
 firstName: [null, Validators.required],
 lastName: [null, Validators.required]
});
}

Each time you reload this component, the first Lifecycle hook triggered is ngOnInIt(), resulting in the reinitialization of your form with firstName and lastName values set to null.

Solution: Introduce a new Class

export class User {
firstName: string,
lastName: string

constructor (data) {
  this.firstName = data.firstName ? data.firstName : '';
  this.lastName = data.lastName ? data.lastName : '';
 }
}

Utilize the above Class to develop a reactive control. Retrieve stored user data from services, create a new user instance, and pass it to the form controls.

userForm: FormGroup
user: User
constructor(private someService: SomeService, private fb: FormBuilder) {}

ngOnInIt() {
 // Obtain user data through service call 
 this.someService.getUser((res) => {
  this.user = new User(res);
  this.createForm();
 });
}

createForm() {
 this.userForm = this.fb.group({
  firstName: [this.user.firstName, Validators.required],
  lastName: [this.user.lastName, Validators.required]
})
}

//by using user = new User(res); If res contains firstName field, it will be assigned to user, otherwise set as an empty string.

I trust this solution is beneficial in resolving the issue.

Answer 4

Lazy loading is not the issue at hand here, for example, if you are utilizing reactive controls in your form,

userForm: FormGroup
constructor (private fb: FormBuilder) {}
ngOnInIt() {
 this.userForm = this.fb.group({
 firstName: [null, Validators.required],
 lastName: [null, Validators.required]
});
}

Each time you reload this component, the first Lifecycle hook triggered is ngOnInIt(), resulting in the reinitialization of your form with firstName and lastName values set to null.

Solution: Introduce a new Class

export class User {
firstName: string,
lastName: string

constructor (data) {
  this.firstName = data.firstName ? data.firstName : '';
  this.lastName = data.lastName ? data.lastName : '';
 }
}

Utilize the above Class to develop a reactive control. Retrieve stored user data from services, create a new user instance, and pass it to the form controls.

userForm: FormGroup
user: User
constructor(private someService: SomeService, private fb: FormBuilder) {}

ngOnInIt() {
 // Obtain user data through service call 
 this.someService.getUser((res) => {
  this.user = new User(res);
  this.createForm();
 });
}

createForm() {
 this.userForm = this.fb.group({
  firstName: [this.user.firstName, Validators.required],
  lastName: [this.user.lastName, Validators.required]
})
}

//by using user = new User(res); If res contains firstName field, it will be assigned to user, otherwise set as an empty string.

I trust this solution is beneficial in resolving the issue.

What is the best way to persist form state in an Angular Lazy Loading Module?

Answer №1

Answer №2

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