AngularJS orderBy expression with subtraction - angularjs

Question

I have an expression
{{ product.SelectedProduct.BasePrice - product.SelectedProduct.Discount | currency }}
I need to be able to order my products by the value of baseprice - discount. Is there a way to do this? So I want something like
{{product.SelectedProduct.ProductName |
orderBy : product.SelectedProduct.BasePrice - product.SelectedProduct.Discount }}
New code:
<div class="row-fluid">
<span class="mktpl_productnm" ng-show="product.SelectedProduct.ProductName">{{product.SelectedProduct.ProductName || 'product not available' | orderBy: price }}</span>
<span ng-hide="product.SelectedProduct.ProductName" class="field-validation-error">Product not available</span>
<span ng-show="product.SelectedProduct.remaining < product.SelectedProduct.prodterm.minQuantity" class="field-validation-error">
(Out of stock)
</span>
</div>
vm.price = function (product) {
debugger;
return product.SelectedProduct.BasePrice - product.SelectedProduct.Discount;
};

Answer 1

First of all, your example doesn't make much sense: orderBy applies to an array, to order the elements of this array. But product.SelectedProduct.ProductName is probably not an array.
Second: the documentation says:
expression function()stringArray.<(function()|string)>=
A predicate to be used by the comparator to determine the order of elements.
Can be one of:
function: Getter function. The result of this function will be sorted using the <, ===, > operator.
[...]
So, all you need is a function in the scope that returns the element to compare for a given element of the array:
$scope.reducedPrice = function(product) {
return product.SelectedProduct.BasePrice - product.SelectedProduct.Discount;
};
and in the view:
{{ productArray | orderBy:reducedPrice }}
Another option would be to precompute the reducedPrice and store it as an attribute or the product, and then simply use
{{ productArray | orderBy:'reducedPrice' }}