The trackBy function (e.g. in an ngFor) provides two arguments: index and item (from the collection being iterated over). Is there a way to pass additional information (as parameters?) to th trackBy function?
My case is that I might be iterating over a variety of types for each instance of my component (which contains the ngFor), with different identifying field names. Ideally, I'd like to be able to pass a third parameter indicating which field in my item should be read.
bind method can help you to do this trick
template.html
<div *ngFor="let item of items; trackBy: trackByFn.bind(this, 'name')">
{{ item }}
</div>
component.ts
items = [
{
id: 1,
name: 'name1'
},
{
id: 2,
name: 'name2'
}
]
trackByFn(customParam, index, item) {
return item[customParam];
}