I have a question about checking if some field in object exists.
I want to print all categories which user has so I\'m doing something like this:
&
basic usage
Use the safe-navigation operator
{{category?.name}}
then name
is only read when category
is not null
.
array
This only works for the .
(dereference) operator.
For an array you can use
{{records && records[0]}}
See also Angular 2 - Cannot read property '0' of undefined error with context ERROR CONTEXT: [object Object]
async pipe
With async
pipe it can be used like
{{(chapters | async)?.length
ngModel
With ngModel
currently it needs to be split into
[ngModel]="details?.firstname" (ngModelChange)="details.firstname = $event"
See also Data is not appending to template in angular2
*ngIf
An alternative is always to wrap the part of the view with *ngIf="data"
to prevent the part being rendered at all before the data
is available to prevent the dereference error.