Limiting upload of number of files in ng-file-upload

ng-file-upload is a wonderful module to help you manage uploading files through AngularJS. Head on over to https://github.com/danialfarid/ng-file-upload to check it out.

One thing that isn’t obvious is how to limit the number of files that a user can upload. (This of course only applies if you are allowing multiple file uploads).

One way to limit the number of files a user can upload is through the “ngf-validate-fn” angular directive. This directive can be used to call a custom function defined in your controller that validates the file.

In this custom validation function, you can check the number of files that already exist in the files model, and return true (meaning validation passed, file should be allowed) or false (or an error name, meaning validation failed… the max number of files has reached).

Let’s say you want to limit the maximum number of files uploaded to 10. It would look like this in your html:

<div ngf-select ngf-multiple="true" ng-model="files" ngf-validate-fn="validateFile($file)" />

And in your controller:

$scope.validateFile = function(file)
{
  if($scope.files.length>=10)
    return "TOO_MANY_FILES";
  return true;
}

And that’ll do it.

HOWEVER, big caveat: This will only work if the user selects one file at a time. If the user selects multiple files all at once (from the file-selection dialog box their browser presents), then this limitation trick will not work, and more files will get through. I am currently in the process of either myself implementing this feature as a native directive in the ng-file-upload module, or waiting till someone else implements it. I’ve posted this as an enhancement request on the module’s github page.