Using Angular 7 to assign values to Input fields while accounting for potential null values

I have been utilizing the code snippet below to populate values in an input field. Setting values of input fields with Angular 6

<input matInput placeholder = "ProductName" [(ngModel)]="orderLine.productname">

However, there are instances where the value could be null. While attempting to handle this by using the question mark ?, I encountered an error. Is it feasible to insert a possible blank or null value into an input field, or is it not achievable?

<input matInput placeholder = "ProductName" [(ngModel)]="orderLine?.productname">

The syntax error occurred when trying to use the '?.' operator for assignment: [[orderLine?.productname=$event]

angulartypescriptangular-materialangular7

Answer №1

Kindly divide it into two sections as both are essential components of ngModel:

[ngModel]="orderLine?.price" (ngModelChange)="orderLine.price = $event"

Answer №2

When it comes to ngModel two-way binding, the use of ?. is not allowed. However, there is an alternate solution using a ternary operator:

<input matInput placeholder = "Price" [(ngModel)]="orderLine? orderLine.price: null">

Answer №3

It is not possible to utilize the ternary operator ? in two-way binding

<input matInput placeholder = "Price" [(ngModel)]="orderLine?.price">

If your orderLine object looks something like this, then there is no need to use this operator...

    orderLine= new OrderLine();

    class OrderLine {
         ...
         price: number;
         ...
    }

Answer №4

For optimal functionality, it is recommended to separate the two-way-binding into a data binding and an event binding:

[ngModel] = "orderLine?.price"
(ngModelChange) = "orderLine.price = $event"

Answer №5

Splitting two-way binding is necessary.

[ngModel]="orderLine?.price" (ngModelChange)="orderLine.price = $event"

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