Angularjs applying $watch to cellTemplate function - angularjs

Question

I am showing data to user using angular ui-grid. In the following code for field 'plan', i add a set of entities by calling the getPlan() function and show it using a cellTemplate in ui-grid columnDefs.
$scope.getPlan = function(rowEntity) {
var plan1Temp = rowEntity.plan1;
var plan2Temp = rowEntity.plan2;
var plan3Temp = rowEntity.plan3;
var plan4Temp = rowEntity.plan4;
var plan5Temp = rowEntity.plan5;
var plan6Temp = rowEntity.plan6;
var plan7Temp = rowEntity.plan7;
var plan8Temp = rowEntity.plan8;
plan = plan1Temp+plan2Temp+plan3Temp+plan4Temp+plan5Temp+plan6Temp+plan7Temp+plan8Temp;
console.log("plan=", plan);
return plan;
};
columnDefs: [{ field : 'plan',
cellTemplate : '<div id="grid-cell-template">
{{grid.appScope.getPlan(row.entity)}}</div>',
displayName : "Plan",
footerCellTemplate : '<div class="ui-grid-cell-contents">
\Total:\ {{grid.appScope.getTotalPlan() }}</div>',
width : "*"
}]
Then to show the total of all the plans i use footerCellTemplate with getTotalPlan(). While using it i got $digest() iterations reached error. I noticed the getPlan() function is called many times. So i added $watch like shown below.
var totalPlan = [];
$scope.$watch(function() {
return plan;
}, function() {
totalPlan.push(plan);
console.log("totalPlan =", totalPlan);
});
$scope.getTotalPlan = function() {
var sum = 0;
angular.forEach(totalPlan ,function(item){
sum = sum + item;
});
return sum;
console.log("getTotalPlan=", sum);
};
After adding $watch also the getPlan() function is called many times. Also in totalPlan[] it holds only 2 values, first null and second one last record value(in total there are 3 records) and prints this value in the ui-grid footercelltemplate. How should i use $watch to make it work right?
So basically the problem is i am not able to insert 'plan' values into totalPlan[ ] and show the total in the grid footer template.
Also i tried using :: inside the expression, the number of getPlan() calling times reduced to half but no luck.