I'm attempting to use template driven forms, binding to a model in the html to a new instance of lets say Person. I've been unsuccessful in creating a proper binding for checkboxes to a single array property on my model.
The idea is data will come from an api or other source, dynamically render checkboxes via *ngFor and bind what is selected to the Person models property which would be an array of numbers. For example:
class Person {
firstName: string;
someCheckboxPropList: number[];
}
and data could be anything really
const dynamicData = [
{ name: 'name1', value: 1 },
{ name: 'name2', value: 2 }
];
my expected output would be something along the lines of [ 1, 2 ] if both values where to be checked and if only the second was checked [ 2 ].
Here's a sample of what the PersonComponent.ts file might look like
@Component({ ... })
export class PersonComponent {
submitted = false;
model = new Person();
constructor() { }
onSubmit(form) {
this.submitted = true;
console.log(form);
}
}
And where I'm at with the components html file.
<form (ngSubmit)="onSubmit(form)" #form="ngForm">
<input type="text" [(ngModel)] name="person.firstName">
<div *ngFor="let dataItem of dynamicData" >
<input
type="checkbox"
ngModel
name="dynamicData"
[value]="dataItem.value">
<label>{{dataItem.name}}</label>
</div>
</form>
This does not work (and is sample code anyway).
the idea is have two things: Person and PersonForm, so,e.g
person={firstName:"Jessy",props:[1,2]
//but
personForm={firstName:"Jessy",props:[true,true]
So, make two functions
createForm(person) {
return {
firstName: person.firstName,
props: this.dynamicData.map(x => person.props.indexOf(x.value) >= 0)
}
}
retrieveData(personForm) {
let props: number[] = [];
personForm.props.forEach((v, index) => {
if (v)
props.push(this.dynamicData[index].value)
}
)
return {
firstName: personForm.firstName,
props: props
}
}
Well, we have already all we need. When we received a person, create a personForm that it's the data we change in the form. In submit simply call to retrieveData to get the value of person.
When we have a person create a personForm,e.g.
this.service.getPerson().subscribe(person=>
{
this.personForm=createForm(person)
}
)
Our form
<form *ngIf="personForm" (submit)="sendData(personForm)">
<input name="firtName" [(ngModel)]="personForm.firstName">
<div *ngFor="let item of dynamicData;let i=index">
<input name="{{'prop'+i}}"
type="checkBox" [(ngModel)]="personForm.props[i]">{{item.name}}
</div>
<button>Submit</button>
</form>
{{personForm|json}}<br/>
{{retrieveData(personForm)|json}}
And our sendData function
sendData(personForm)
{
console.log(this.retrieveData(personForm))
}
I make a simple stackblitz
Update
NOTE:We can use the spred operator to asing properties, so
createForm(person) {
return {
...person, //All the properties of person, but
props: this.dynamicData.map(x => person.props.indexOf(x.value) >= 0)
}
}
retrieveData(personForm) {
let props: number[] = [];
personForm.props.forEach((v, index) => {
if (v)
props.push(this.dynamicData[index].value)
}
)
return {
..personForm, //all the properties of personForm, but
props: props
}
}
NOTE2: In a "real world" the persons goes from a service. Consider the idea that service get/received the "personForm" and put the functions to transform in the service
//in service
getPerson()
{
return this.httpClient.get("...").map(res=>this.createForm(res))
}
savePerson(personForm)
{
return this.httpClient.post("...",this.retrieveData(personForm))
}
If we want, we can make a custom Form control.
In this case we need as input, a source, and the cols of the source -the first will be the key, and the second one the text that appears.
I make a stackblitz
the .html will be
<check-box-group name="props" [(ngModel)]="person.props"
[source]="dynamicData" cols="value,name" >
</check-box-group>
the component it's a tipical custom form control
@Component({
selector: 'check-box-group',
template: `
<div class="form-check" *ngFor="let item of source;let i=index">
<input class="form-check-input" id="{{_name+''+i}}"
type="checkBox" [ngModel]="_selectedItems[i]"
(ngModelChange)="setValue($event,i)">
<label class="form-check-label" for="{{_name+''+i}}">
{{item[_col]}}
</label>
</div>
`,
providers: [
{
provide: NG_VALUE_ACCESSOR,
useExisting: forwardRef(() => CheckBoxGroupComponent),
multi: true
}
]
})
export class CheckBoxGroupComponent implements ControlValueAccessor {
@Input() source;
@Input()
set cols(value:string){ //cols is a string separated by commas
//e.g. "value,text", the "key" will be "value" and show the text
let _cols=value.split(',')
this._key = _cols[0];
this._col = _cols[1]
}
_selectedItems: any[] = [];
_key: string;
_col: string;
_name:string="";
onChange;
onTouched;
constructor(el:ElementRef) {
let name=el.nativeElement.getAttribute('name')
this._name=name?name:"ck";
}
writeValue(value: any[]): void {
this._selectedItems = this.propsToBoolean(value);
}
registerOnChange(fn: any): void {
this.onChange = fn;
}
registerOnTouched(fn: any): void {
this.onTouched = fn;
}
setDisabledState(isDisabled: boolean): void {
}
setValue(value: boolean, index: number) {
this._selectedItems[index] = value;
this.onChange(this.booleanToProps(this._selectedItems));
}
propsToBoolean(props): any[] {
console.log(props);
return props ? this.source.map((x: any) => props.indexOf(x[this._key]) >= 0)
: this.source.map(x => false);
}
booleanToProps(propsBoolean: boolean[]) {
let props: any[] = [];
if (propsBoolean) {
propsBoolean.forEach((item, index) => {
if (item)
props.push(this.source[index][this._key])
})
}
return props;
}
}
Update: add validations
when we have a custom form component and we want to make a "validation" we have two options, make the validation outside the component or make a validation inside the component. For the second option we must to add as provider provide: NG_VALIDATORS,,
{
provide: NG_VALIDATORS,
useExisting: forwardRef(() => CheckBoxGroupComponent),
multi: true,
}
And add a function validate
validate(control: AbstractControl): ValidationErrors | null{
...your logic here.., e.g.
if (!this._selectedItems.find(x=>x))
return {error:"you must select one option at last"}
return null
}
Well, there're a more thing we must to do that is decide when our custom control are touched. Remember that a control is touched when lost the focus after received it. we can do it in a (blur) of our checkbox (or enclose the control in a div with tabindex=0)
<input type="checkbox" .... (blur)="onTouched()">
The last step is make give an error or not is we add an attribute to the control. I like that if we add an attribute isRequired, check the error else not. So we add a new property _isRequired and, in contructor check if has the attribute
constructor(el:ElementRef) {
let name=el.nativeElement.getAttribute('name');
this._isRequired=el.nativeElement.getAttribute('isRequired')!=null?true:false;
this._name=name?name:"ck"; //<--this is necesary for give value to
//for="..." in label
}
And our validation take account of this
validate(control: AbstractControl): ValidationErrors | null{
if (!this._isRequired)
return null;
....
}
NOTE: I updated the custom control (and we add a propertie [customClass])
