Angular - direct binding to a function

Question

are there any negative (performance) implications of binding directly to a function in e. g. ng-show directive?

<div ng-show="myVm.isVisible()">
....
</div>

// controller snippet (exposed through controllerAs syntax)
function myCtrl (myService, authService) {
  this.isVisible = function isVisible () {
    return (myService.state === 'foo' && authService.isAuthorised);
  }
}

this pattern allows hiding sometimes complex logic in the template and putting in the testable controller (or service) but some developers seem to be worried about binding a function in directives like ng-show, ng-if etc.

bahadir · Accepted Answer · 2015-05-26 13:51:46Z

2

actually it is mostly about complexity of your function. angular calls your function on every digest cycle and compares with it's previous value. of course it is slower than checking a simple variable. so you could say it has negative performance implications. if performance is a big issue on this function (lets say your function takes too much time to compute). you can store output of your function to a variable, check that variable on template and change that variable when it is required to.

answered May 26, 2015 at 13:51

bahadir

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