AngulaJS filter on array of object - angularjs

Question

I have this JSON object.
var UsersList=[
{
"User" : {
"IdUser" : "admin",
"FirstName" : "mirco",
"LastName" : "sabatino"
}
}, {
"User" : {
"IdUser" : "coordinator",
"FirstName" : "coordinator",
"LastName" : ""
}
}, {
"User" : {
"IdUser" : "test",
"FirstName" : "publisher",
"LastName" : "Diaz"
}
}, {
"User" : {
"IdUser" : "work",
"FirstName" : "ingester",
"LastName" : "Brown"
}
}
] ;
I want filter in ng-repeat for LastName value.
<div class="col-md-6" ng-repeat="users in UsersList | filter: {User.LastName : filterSearchLetter}">
filterSearchLetter value in my controler is populated by
$scope.filterLetterUser=function(letter){
$scope.filterSearchLetter=letter;
console.log($scope.filterSearchLetter);
};
But this don't work.

Answer 1

See my plnkr for the solution http://plnkr.co/edit/l27xUQ?p=preview. I also have implemented your required UI behavior using ng-change. Hope it helps.
For detailed explanation I offer you Todd Motto's blog - http://toddmotto.com/everything-about-custom-filters-in-angular-js/
To invoke a filter, the syntax is the filter function name followed by the parameters.
To define a filter you need to do (This is copy of Todd Motto's code modified for your data)
todos.filter('startsWithLetter', function () {
return function (items, letter) {
var filtered = [];
var letterMatch = new RegExp(letter, 'i');
for (var i = 0; i < items.length; i++) {
var item = items[i];
if (letterMatch.test(item.User.LastName.substring(0, 1))) {
filtered.push(item);
}
}
return filtered;
};
});

Answer 2

This is not a valid object: {User.LastName : filterSearchLetter} It should actually throw an exception saying something like
Uncaught SyntaxError: Unexpected token .
What you probably want to try instead is: {"User": {"LastName" : filterSearchLetter} }

Answer 3

To iterate over an array of Objects see:
angularjs - ng-repeat: access key and value from JSON array object
You may have to convert to valid JS object using JS_Obj=JSON.parse(JSON_Obj);
Maybe something like this:
//iterate through array
<ul ng-repeat="users in UsersList">
//iterate through Object
<li ng-repeat=(key, value) in users | filter: {User.LastName : filterSearchLetter}>
{{key}} : {{value}}
</li>
</ul>