Suggestions UI - expandable item

ios/chrome/browser/ui/suggestions/suggestions_expandable_item.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef IOS_CHROME_BROWSER_UI_SUGGESTIONS_SUGGESTIONS_EXPANDABLE_ITEM_H_
+#define IOS_CHROME_BROWSER_UI_SUGGESTIONS_SUGGESTIONS_EXPANDABLE_ITEM_H_
+
+#import "ios/third_party/material_components_ios/src/components/CollectionCells/src/MaterialCollectionCells.h"
+
+#import "ios/chrome/browser/ui/collection_view/cells/collection_view_item.h"
+
+// Item for an expandable article in the suggestions. An expandable article can
+// be expanded, displaying more informations/interactions.
+@interface SuggestionsExpandableItem : CollectionViewItem
+
+// Init the article with a |title|, a |subtitle| an |image| and some |detail|
+// displayed only when the article is expanded. |type| is the type of the item.
+- (instancetype)initWithType:(NSInteger)type
+                       title:(NSString*)title
+                    subtitle:(NSString*)subtitle
+                       image:(UIImage*)image
+                  detailText:(NSString*)detail NS_DESIGNATED_INITIALIZER;
+
+- (instancetype)initWithType:(NSInteger)type NS_UNAVAILABLE;
+
+// The collectionView displaying this article. Its layout will be invalidated
+// when the article is expanded/retracted.
+@property(nonatomic, assign) UICollectionView* collectionView;

[lpromero, 2017/01/11 13:19:20]

Don't depend on the collection like this. Have a delegate on the cell is that
notified of UI events, then the delegate can do this.
Keep the item out of the loop. You can set the delegate in
~cellForItemAtIndexPath.

[gambard, 2017/01/12 14:39:40]

It means inspecting the type of every cell in the collection to check if they
are SuggestionsExpandableCell. This seems a bit extreme.

[lpromero, 2017/01/12 16:44:38]

Don't check the cell type, check the ItemType for the index path. That's what we
always do in these -collectionView:cellForItemAtIndexPath: methods.
Having the item depend on the collection view is a show-stopper. It is the
controller's job to handle the relationship between item and cell, even if that
means more code in the controller.

We sometimes call that "dumb item", or "dumb cell", where they don't
communicate.

+
+@end
+
+// Corresponding cell of an expandable article.
+@interface SuggestionsExpandableCell : MDCCollectionViewCell
+
+@property(nonatomic, assign) SuggestionsExpandableItem* item;

[lpromero, 2017/01/11 13:19:20]

I'd remove this and keep the item just as a data holder. Collection and cell can
talk to each other in ~cellForItemAtIndexPath and delegate callbacks.

[gambard, 2017/01/12 14:39:40]

The item needs to know if the cell has been expanded or not to adjust the height
(calling expand or retract on the sizing cell).

[lpromero, 2017/01/12 16:44:38]

The item should hold that knowledge. In its public interface.
Ideally, the item should be sufficient to recreate a cell from the ground up.

+@property(nonatomic, copy) NSString* title;
+@property(nonatomic, copy) NSString* subtitle;
+@property(nonatomic, copy) NSString* detail;
+@property(nonatomic, retain) UIImage* image;
+
+@end
+
+#endif  // IOS_CHROME_BROWSER_UI_SUGGESTIONS_SUGGESTIONS_EXPANDABLE_ITEM_H_