How to validate a form in a ionic slide before moving to next slide?

Question

I am building an ionic app with 4 slides with forms in each slide using slideNext() to move to the next slides. Is there a way I could validate each slide form before moving to the next slide? I would attempt an 'if' statement to check the validity of the slides at the last slide before submitting all the form data but some forms need user inputs from earlier slides so the forms need to be validated at slide change. How can I do this?

Answer 1

I have this function that check my form fields validity.

    /**
     * Return boolean indicating current slides validity
     */
    public hIsCurrentSlideValid(): boolean {
        /* Use the current active slide to determine if the datafield being displayed on that slide has error checks */
        let lAnyErrorChecks = this.myForm.controls[this.hActiveSlideIndex].errors;

        /* If there are error check, ensure that error check is the required field and is active else enable the button */
        return lAnyErrorChecks ? (lAnyErrorChecks.required as boolean) : false;
    }

Just to make things a little more complicated the active index check return a promise so that cant be used in html without triggering a endless loop of updates

So I had to add a function that stores the Active index off the slide when the slide is changed

    /**
     * Return values of current slide on change
     */
    public hCheckSlidesOnChange() {
        let lPromiseBeginSlide = this.slides.isBeginning();
        let lPromiseEndSlide = this.slides.isEnd();
        /* Get the current active slide */
        let lPromiseActiveIndex = this.slides.getActiveIndex();

        Promise.all([lPromiseBeginSlide, lPromiseEndSlide, lPromiseActiveIndex]).then((aPromiseReturn) => {
            aPromiseReturn[0]
                ? (this.disablePreviousButton = true)
                : (this.disablePreviousButton = false);
            aPromiseReturn[1] ? (this.disableNextButton = true) : (this.hSlidesDisableNextButton = false);

            /* Get the current active slide */
            this.hActiveSlideIndex = aPromiseReturn[2];
        });
    }

For completeness here is my global variables.

@ViewChild("mySlides") slides;

public myForm: FormGroup = new FormGroup({});
public disableNextButton: boolean = false;
public disablePreviousButton: boolean = true;
public hActiveSlideIndex: number = 0;

Here is my HTML

<form id="data-collector" [formGroup]="myForm">
    <ion-slides #mySlides (ionSlideWillChange)="hCheckSlidesOnChange()">
        <ion-slide *ngFor="let myValue of myValues" class="form-row">
            <myinputComponent></myinputComponent>
        </ion-slide>
    </ion-slides>
</form>
                
<ion-footer>
    <ion-button slot="start"
                [disabled]="mySlides ? disablePreviousButton : true"
                (click)="mySlides.slidePrev()">Previous</ion-button>
    <ion-button slot="end"
                [hidden]="mySlides ? disableNextButton : true"
                [disabled]="hIsCurrentSlideValid()" (click)="mySlides.slideNext()">Next</ion-button>
    <ion-button form="data-collector" slot="end" type="submit" 
                [hidden]="mySlides ? !disableNextButton : true" [disabled]="isFormValid" (click)="Save()">
                Save
            </ion-button>
</ion-footer>

Let me know if there is anything that is unclear, but yea this is working for me