angular自定义directive [filelistread]: 多文件上传，解决ngModel读不了上传文件的问题，并补充limit数量限制

angular-directive-filelistread.js

/**
 * usage:
 * <form name="form">
 *   <input type="file" multiple name="uploads" filelistread limit="8" ng-model="uploads" />
 *   <label ng-show="form.uploads.$error.limit">上传文件数量限制最多为8个</label>
 * </form>
 */
angular.module('testapp', []).directive("filelistread", function() {
		return {
			require: 'ngModel',
			scope: {
				limit: '@',
				// filelistread: '='
				// ngModel: '='
			},
			link: function(scope, elem, attr, ctrl) {
				elem.bind('change', function(changeEvent) {
					scope.$apply(function() {
						ctrl.$setViewValue(changeEvent.target.files);
						if (ctrl.$viewValue.length > scope.limit) {
							ctrl.$setValidity('limit', false);
						} else {
							ctrl.$setValidity('limit', true);
						}
					});
				});
			}
		};
	})