GEEKING

iOS/RobloxUI/Source/Components/RBInfiniteTableView.m

@@ -0,0 +1,193 @@
+//
+//  RBInfiniteTableView.m
+//  RobloxMobile
+//
+//  Created by Ariel Lichtin on 10/14/14.
+//  Copyright (c) 2014 ROBLOX. All rights reserved.
+//
+
+#import "RBInfiniteTableView.h"
+
+#define NUM_ITEMS_PER_REQUEST 20
+#define START_REQUEST_THRESHOLD 10 // The next request will start when there are 10 elements left
+
+@interface RBInfiniteTableView () <UITableViewDelegate, UITableViewDataSource>
+
+@end
+
+@implementation RBInfiniteTableView
+{
+    NSUInteger _numItemsInView;
+    BOOL _requestInProgress;
+    BOOL _listComplete;
+}
+
+- (id)initWithCoder:(NSCoder *)aDecoder
+{
+    self = [super initWithCoder:aDecoder];
+    if(self)
+    {
+        [self initTableView];
+    }
+    return self;
+}
+
+- (instancetype)initWithFrame:(CGRect)frame
+{
+    self = [super initWithFrame:frame];
+    if(self)
+    {
+        [self initTableView];
+    }
+    return self;
+}
+
+- (instancetype)initWithFrame:(CGRect)frame style:(UITableViewStyle)style
+{
+    self = [super initWithFrame:frame style:style];
+    if(self)
+    {
+        [self initTableView];
+    }
+    return self;
+}
+
+- (void)initTableView
+{
+    _numItemsInView = NUM_ITEMS_PER_REQUEST;
+    _listComplete = NO;
+    _requestInProgress = NO;
+    
+    __weak RBInfiniteTableView* weakSelf = self;
+    self.delegate = weakSelf;
+    self.dataSource = weakSelf;
+    
+    [self reloadData];
+}
+
+- (void)scrollViewDidScroll:(UIScrollView *)scrollView
+{
+    // Get the index of the last visible item
+    NSArray* indexes = [self indexPathsForVisibleRows];
+    NSIndexPath* maxIndex = nil;
+    for(NSIndexPath* index in indexes)
+    {
+        if(maxIndex == nil || maxIndex.row < index.row)
+        {
+            maxIndex = index;
+        }
+    }
+    
+    if(_listComplete == NO && maxIndex.row + START_REQUEST_THRESHOLD > _numItemsInView)
+    {
+        _numItemsInView += NUM_ITEMS_PER_REQUEST;
+        
+        NSMutableArray* indexes = [NSMutableArray array];
+        for(NSUInteger i = _numItemsInView - NUM_ITEMS_PER_REQUEST; i < _numItemsInView; ++i)
+        {
+            [indexes addObject:[NSIndexPath indexPathForRow:i inSection:0]];
+        }
+
+        [self beginUpdates];
+        [self insertRowsAtIndexPaths:indexes withRowAnimation:UITableViewRowAnimationAutomatic];
+        [self endUpdates];
+        
+        [self loadElementsAsync];
+    }
+}
+
+- (void)loadElementsAsync
+{
+    if(_infiniteDelegate == nil)
+        return;
+    
+    NSUInteger itemCount = [_infiniteDelegate numItemsInInfiniteTableView:self];
+    if(!_listComplete && !_requestInProgress && _numItemsInView > itemCount)
+    {
+        _requestInProgress = YES;
+
+        NSUInteger itemsToRequest = _numItemsInView - itemCount;
+
+        void(^block)() = ^()
+        {
+            NSUInteger newItemCount = [_infiniteDelegate numItemsInInfiniteTableView:self];
+            
+            NSInteger rangeFrom = itemCount;
+            NSInteger rangeTo = newItemCount;
+            
+            // Update visible elements
+            NSArray* visibleCells = [self indexPathsForVisibleRows];
+            if(visibleCells.count > 0)
+            {
+                NSMutableArray* cellsToUpdate = [NSMutableArray array];
+                for(NSIndexPath* indexPath in visibleCells)
+                {
+                    BOOL inRange = indexPath.row >= rangeFrom && indexPath.row < rangeTo;
+                    if(inRange)
+                        [cellsToUpdate addObject:indexPath];
+                }
+                [self reloadRowsAtIndexPaths:cellsToUpdate withRowAnimation:UITableViewRowAnimationAutomatic];
+            }
+            
+            NSUInteger numItemsRetrieved = newItemCount - itemCount;
+            _listComplete = numItemsRetrieved < itemsToRequest;
+            if(_listComplete)
+            {
+                // If the list is already complete,
+                // remove the remaining placeholder empty cells
+                NSUInteger totalElements = _numItemsInView;
+                
+                _numItemsInView = newItemCount;
+                
+                NSMutableArray* indexes = [NSMutableArray array];
+                for(NSUInteger i = newItemCount; i < totalElements; ++i)
+                {
+                    [indexes addObject:[NSIndexPath indexPathForRow:i inSection:0]];
+                }
+                
+                [self beginUpdates];
+                [self deleteRowsAtIndexPaths:indexes withRowAnimation:UITableViewRowAnimationAutomatic];
+                [self endUpdates];
+            }
+            
+            _requestInProgress = NO;
+            
+            [self loadElementsAsync];
+        };
+        
+        [_infiniteDelegate asyncRequestItemsForTableView:self numItemsToRequest:itemsToRequest completionHandler:block];
+    }
+}
+
+- (NSUInteger)numItems
+{
+    return _numItemsInView;
+}
+
+- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
+{
+    return 1;
+}
+
+- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
+{
+    return _numItemsInView;
+}
+
+- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
+{
+    if(_infiniteDelegate)
+        return [_infiniteDelegate infiniteTableView:self cellForItemAtIndexPath:indexPath];
+    else
+        return nil;
+}
+
+- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
+{
+    if(_infiniteDelegate)
+    {
+        [_infiniteDelegate infiniteTableView:self didSelectItemAtIndexPath:indexPath];
+    }
+}
+
+@end