new format for the dataset.get method

Author: mfeingold

demo/examples/scopeDatasource.coffee

@@ -5,9 +5,11 @@ angular.module('application', ['ui.scroll', 'ui.scroll.jqlite']).controller('mai
 
 				datasource = {}
 
-				datasource.get = (index, count, success)->
+				datasource.get = (descriptor, success)->
 					$timeout(
 						->
+							index = descriptor.index
+							count = descriptor.count
 							result = []
 							for i in [index..index + count-1]
 								result.push "item ##{i}"

src/ui-scroll.coffee

@@ -506,13 +506,27 @@ angular.module('ui.scroll', [])
 						else
 							fetch(rid)
 
+				if datasource.get.length == 2
+					fetchNext = (success) -> datasource.get
+							index: buffer.next
+							append: if buffer.length then buffer[buffer.length-1].item else undefined
+							count: bufferSize
+							success
+					fetchPrevious = (success) -> datasource.get
+							index: buffer.first-bufferSize
+							prepend: if buffer.length then buffer[0].item else undefined
+							count: bufferSize
+							success
+				else
+					fetchNext = (success) -> datasource.get buffer.next, bufferSize, success
+					fetchPrevious = (success) -> datasource.get buffer.first-bufferSize, bufferSize, success
+
 				fetch = (rid) ->
 					if pending[0] # scrolling down
 						if buffer.length && !viewport.shouldLoadBottom()
 							adjustBufferAfterFetch rid
 						else
-							datasource.get buffer.next, bufferSize,
-							(result) ->
+							fetchNext (result) ->
 								return if (rid and rid isnt ridActual) or $scope.$$destroyed
 								if result.length < bufferSize
 									buffer.eof = true
@@ -526,8 +540,7 @@ angular.module('ui.scroll', [])
 						if buffer.length && !viewport.shouldLoadTop()
 							adjustBufferAfterFetch rid
 						else
-							datasource.get buffer.first-bufferSize, bufferSize,
-							(result) ->
+							fetchPrevious (result) ->
 								return if (rid and rid isnt ridActual) or $scope.$$destroyed
 								if result.length < bufferSize
 									buffer.bof = true

test/BasicSetupSpec.js

@@ -60,11 +60,38 @@ describe('uiScroll', function () {
                 runTest(scrollSettings,
                     function () {
                         expect(spy.calls.all().length).toBe(2);
+                        expect(spy.calls.all()[0].args.length).toBe(3);
                         expect(spy.calls.all()[0].args[0]).toBe(1);
+                        expect(spy.calls.all()[0].args[1]).toBe(10);
+                        expect(spy.calls.all()[1].args.length).toBe(3);
                         expect(spy.calls.all()[1].args[0]).toBe(-9);
+                        expect(spy.calls.all()[1].args[1]).toBe(10);
                     }
                 );
             });
         });
 
+    describe('basic setup (new datasource get signature)', function () {
+        var scrollSettings = {datasource: 'myNewEmptyDatasource'};
+
+        return;
+        // this does not work because spy always return 0 for the number of parameters (spy.length)
+        it('should call get on the datasource 2 times ', function () {
+            var spy;
+            inject(function (myNewEmptyDatasource) {
+                spy = spyOn(myNewEmptyDatasource, 'get').and.callThrough();
+            });
+            runTest(scrollSettings,
+                function () {
+                    expect(spy.calls.all().length).toBe(2);
+                    expect(spy.calls.all()[0].args.length).toBe(2);
+                    expect(spy.calls.all()[0].args[0].index).toBe(1);
+                    expect(spy.calls.all()[0].args[0].count).toBe(10);
+                    expect(spy.calls.all()[0].args.length).toBe(2);
+                    expect(spy.calls.all()[1].args[0]).index.toBe(-9);
+                    expect(spy.calls.all()[1].args[0].count).toBe(10);
+                }
+            );
+        });
+    });
 });

test/BasicTestsSpec.js

@@ -161,8 +161,6 @@ describe('uiScroll', function () {
         it('should clip 3 divs from the top and add 3 more divs to the bottom (9 divs total) (+ 2 padding divs)', function () {
             runTest(scrollSettings,
                 function (viewport, scope, $timeout) {
-// padding calculations are different now, besides the specific number of elements clipped
-// is not that important and a test for cliptop/bottom methods of the viewport object is more appropriate
                     viewport.scrollTop(100);
                     viewport.trigger('scroll');
                     $timeout.flush();

test/datasources.js

@@ -10,6 +10,16 @@ angular.module('ui.scroll.test.datasources', [])
         }
     ])
 
+    .factory('myNewEmptyDatasource', [
+        '$log', '$timeout', '$rootScope', function () {
+            return {
+                get: function (descriptor, success) {
+                    success([]);
+                }
+            };
+        }
+    ])
+
     .factory('myOnePageDatasource', [
         '$log', '$timeout', '$rootScope', function () {
             return {