Conditional expression requires all 3 expressions at the end

Question

<div *ngFor="let f of layout?.photoframes; let i = index" [attr.data-index]="i">
   <input type="number" [(ngModel)]="f.x" [style.border-color]="(selectedObject===f) ? 'red'"  />
</div>

the conditional style throws the error

Conditional expression (selectedObject===f) ? 'red' requires all 3 expressions at the end
of the expression [(selectedObject===f) ? 'red'] what can I do?

Answer 1

You need also to pass the result of the case in which condition will return false. In other words you need to pass correct ternary operator

Something like if/else. If true return red, else return blue.

(selectedObject === f) ? 'red' : 'blue'

Answer 2

This applies to a different context, but if you are using a pipe ( | ) in Angular and you get this error from your view you may need to put parentheses around your pipe like this:

<input value={{device.id ? (device.id | decimalToHex) : ''}}>

if you leave them off like this:

<input value={{device.id ? device.id | decimalToHex : ''}}>

Then you get this error