UITableView+FDTemplateLayoutCell.m

// The MIT License (MIT)
//
// Copyright (c) 2015-2016 forkingdog ( https://github.com/forkingdog )
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#import "UITableView+FDTemplateLayoutCell.h"
#import <objc/runtime.h>

@implementation UITableView (FDTemplateLayoutCell)

- (CGFloat)fd_systemFittingHeightForConfiguratedCell:(UITableViewCell *)cell {
    CGFloat contentViewWidth = CGRectGetWidth(self.frame);
    
    // If a cell has accessory view or system accessory type, its content view's width is smaller
    // than cell's by some fixed values.
    if (cell.accessoryView) {
        contentViewWidth -= 16 + CGRectGetWidth(cell.accessoryView.frame);
    } else {
        static const CGFloat systemAccessoryWidths[] = {
            [UITableViewCellAccessoryNone] = 0,
            [UITableViewCellAccessoryDisclosureIndicator] = 34,
            [UITableViewCellAccessoryDetailDisclosureButton] = 68,
            [UITableViewCellAccessoryCheckmark] = 40,
            [UITableViewCellAccessoryDetailButton] = 48
        };
        contentViewWidth -= systemAccessoryWidths[cell.accessoryType];
    }
    
    // If not using auto layout, you have to override "-sizeThatFits:" to provide a fitting size by yourself.
    // This is the same height calculation passes used in iOS8 self-sizing cell's implementation.
    //
    // 1. Try "- systemLayoutSizeFittingSize:" first. (skip this step if 'fd_enforceFrameLayout' set to YES.)
    // 2. Warning once if step 1 still returns 0 when using AutoLayout
    // 3. Try "- sizeThatFits:" if step 1 returns 0
    // 4. Use a valid height or default row height (44) if not exist one
    
    CGFloat fittingHeight = 0;
    
    if (!cell.fd_enforceFrameLayout && contentViewWidth > 0) {
        // Add a hard width constraint to make dynamic content views (like labels) expand vertically instead
        // of growing horizontally, in a flow-layout manner.
        NSLayoutConstraint *widthFenceConstraint = [NSLayoutConstraint constraintWithItem:cell.contentView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:contentViewWidth];

        // [bug fix] after iOS 10.3, Auto Layout engine will add an additional 0 width constraint onto cell's content view, to avoid that, we add constraints to content view's left, right, top and bottom.
        static BOOL isSystemVersionEqualOrGreaterThen10_2 = NO;
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            isSystemVersionEqualOrGreaterThen10_2 = [UIDevice.currentDevice.systemVersion compare:@"10.2" options:NSNumericSearch] != NSOrderedAscending;
        });
        
        NSArray<NSLayoutConstraint *> *edgeConstraints;
        if (isSystemVersionEqualOrGreaterThen10_2) {
            // To avoid confilicts, make width constraint softer than required (1000)
            widthFenceConstraint.priority = UILayoutPriorityRequired - 1;
            
            // Build edge constraints
            NSLayoutConstraint *leftConstraint = [NSLayoutConstraint constraintWithItem:cell.contentView attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:cell attribute:NSLayoutAttributeLeft multiplier:1.0 constant:0];
            NSLayoutConstraint *rightConstraint = [NSLayoutConstraint constraintWithItem:cell.contentView attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:cell attribute:NSLayoutAttributeRight multiplier:1.0 constant:0];
            NSLayoutConstraint *topConstraint = [NSLayoutConstraint constraintWithItem:cell.contentView attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:cell attribute:NSLayoutAttributeTop multiplier:1.0 constant:0];
            NSLayoutConstraint *bottomConstraint = [NSLayoutConstraint constraintWithItem:cell.contentView attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:cell attribute:NSLayoutAttributeBottom multiplier:1.0 constant:0];
            edgeConstraints = @[leftConstraint, rightConstraint, topConstraint, bottomConstraint];
            [cell addConstraints:edgeConstraints];
        }
        
        [cell.contentView addConstraint:widthFenceConstraint];

        // Auto layout engine does its math
        fittingHeight = [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;
        
        // Clean-ups
        [cell.contentView removeConstraint:widthFenceConstraint];
        if (isSystemVersionEqualOrGreaterThen10_2) {
            [cell removeConstraints:edgeConstraints];
        }
        
        [self fd_debugLog:[NSString stringWithFormat:@"calculate using system fitting size (AutoLayout) - %@", @(fittingHeight)]];
    }
    
    if (fittingHeight == 0) {
#if DEBUG
        // Warn if using AutoLayout but get zero height.
        if (cell.contentView.constraints.count > 0) {
            if (!objc_getAssociatedObject(self, _cmd)) {
                NSLog(@"[FDTemplateLayoutCell] Warning once only: Cannot get a proper cell height (now 0) from '- systemFittingSize:'(AutoLayout). You should check how constraints are built in cell, making it into 'self-sizing' cell.");
                objc_setAssociatedObject(self, _cmd, @YES, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
            }
        }
#endif
        // Try '- sizeThatFits:' for frame layout.
        // Note: fitting height should not include separator view.
        fittingHeight = [cell sizeThatFits:CGSizeMake(contentViewWidth, 0)].height;
        
        [self fd_debugLog:[NSString stringWithFormat:@"calculate using sizeThatFits - %@", @(fittingHeight)]];
    }
    
    // Still zero height after all above.
    if (fittingHeight == 0) {
        // Use default row height.
        fittingHeight = 44;
    }
    
    // Add 1px extra space for separator line if needed, simulating default UITableViewCell.
    if (self.separatorStyle != UITableViewCellSeparatorStyleNone) {
        fittingHeight += 1.0 / [UIScreen mainScreen].scale;
    }
    
    return fittingHeight;
}

- (__kindof UITableViewCell *)fd_templateCellForReuseIdentifier:(NSString *)identifier {
    NSAssert(identifier.length > 0, @"Expect a valid identifier - %@", identifier);
    
    NSMutableDictionary<NSString *, UITableViewCell *> *templateCellsByIdentifiers = objc_getAssociatedObject(self, _cmd);
    if (!templateCellsByIdentifiers) {
        templateCellsByIdentifiers = @{}.mutableCopy;
        objc_setAssociatedObject(self, _cmd, templateCellsByIdentifiers, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }
    
    UITableViewCell *templateCell = templateCellsByIdentifiers[identifier];
    
    if (!templateCell) {
        templateCell = [self dequeueReusableCellWithIdentifier:identifier];
        NSAssert(templateCell != nil, @"Cell must be registered to table view for identifier - %@", identifier);
        templateCell.fd_isTemplateLayoutCell = YES;
        templateCell.contentView.translatesAutoresizingMaskIntoConstraints = NO;
        templateCellsByIdentifiers[identifier] = templateCell;
        [self fd_debugLog:[NSString stringWithFormat:@"layout cell created - %@", identifier]];
    }
    
    return templateCell;
}

- (CGFloat)fd_heightForCellWithIdentifier:(NSString *)identifier configuration:(void (^)(id cell))configuration {
    if (!identifier) {
        return 0;
    }
    
    UITableViewCell *templateLayoutCell = [self fd_templateCellForReuseIdentifier:identifier];
    
    // Manually calls to ensure consistent behavior with actual cells. (that are displayed on screen)
    [templateLayoutCell prepareForReuse];
    
    // Customize and provide content for our template cell.
    if (configuration) {
        configuration(templateLayoutCell);
    }
    
    return [self fd_systemFittingHeightForConfiguratedCell:templateLayoutCell];
}

- (CGFloat)fd_heightForCellWithIdentifier:(NSString *)identifier cacheByIndexPath:(NSIndexPath *)indexPath configuration:(void (^)(id cell))configuration {
    if (!identifier || !indexPath) {
        return 0;
    }
    
    // Hit cache
    if ([self.fd_indexPathHeightCache existsHeightAtIndexPath:indexPath]) {
        [self fd_debugLog:[NSString stringWithFormat:@"hit cache by index path[%@:%@] - %@", @(indexPath.section), @(indexPath.row), @([self.fd_indexPathHeightCache heightForIndexPath:indexPath])]];
        return [self.fd_indexPathHeightCache heightForIndexPath:indexPath];
    }
    
    CGFloat height = [self fd_heightForCellWithIdentifier:identifier configuration:configuration];
    [self.fd_indexPathHeightCache cacheHeight:height byIndexPath:indexPath];
    [self fd_debugLog:[NSString stringWithFormat: @"cached by index path[%@:%@] - %@", @(indexPath.section), @(indexPath.row), @(height)]];
    
    return height;
}

- (CGFloat)fd_heightForCellWithIdentifier:(NSString *)identifier cacheByKey:(id<NSCopying>)key configuration:(void (^)(id cell))configuration {
    if (!identifier || !key) {
        return 0;
    }
    
    // Hit cache
    if ([self.fd_keyedHeightCache existsHeightForKey:key]) {
        CGFloat cachedHeight = [self.fd_keyedHeightCache heightForKey:key];
        [self fd_debugLog:[NSString stringWithFormat:@"hit cache by key[%@] - %@", key, @(cachedHeight)]];
        return cachedHeight;
    }
    
    CGFloat height = [self fd_heightForCellWithIdentifier:identifier configuration:configuration];
    [self.fd_keyedHeightCache cacheHeight:height byKey:key];
    [self fd_debugLog:[NSString stringWithFormat:@"cached by key[%@] - %@", key, @(height)]];
    
    return height;
}

@end

@implementation UITableView (FDTemplateLayoutHeaderFooterView)

- (__kindof UITableViewHeaderFooterView *)fd_templateHeaderFooterViewForReuseIdentifier:(NSString *)identifier {
    NSAssert(identifier.length > 0, @"Expect a valid identifier - %@", identifier);
    
    NSMutableDictionary<NSString *, UITableViewHeaderFooterView *> *templateHeaderFooterViews = objc_getAssociatedObject(self, _cmd);
    if (!templateHeaderFooterViews) {
        templateHeaderFooterViews = @{}.mutableCopy;
        objc_setAssociatedObject(self, _cmd, templateHeaderFooterViews, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }
    
    UITableViewHeaderFooterView *templateHeaderFooterView = templateHeaderFooterViews[identifier];
    
    if (!templateHeaderFooterView) {
        templateHeaderFooterView = [self dequeueReusableHeaderFooterViewWithIdentifier:identifier];
        NSAssert(templateHeaderFooterView != nil, @"HeaderFooterView must be registered to table view for identifier - %@", identifier);
        templateHeaderFooterView.contentView.translatesAutoresizingMaskIntoConstraints = NO;
        templateHeaderFooterViews[identifier] = templateHeaderFooterView;
        [self fd_debugLog:[NSString stringWithFormat:@"layout header footer view created - %@", identifier]];
    }
    
    return templateHeaderFooterView;
}

- (CGFloat)fd_heightForHeaderFooterViewWithIdentifier:(NSString *)identifier configuration:(void (^)(id))configuration {
    UITableViewHeaderFooterView *templateHeaderFooterView = [self fd_templateHeaderFooterViewForReuseIdentifier:identifier];
    
    NSLayoutConstraint *widthFenceConstraint = [NSLayoutConstraint constraintWithItem:templateHeaderFooterView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:CGRectGetWidth(self.frame)];
    [templateHeaderFooterView addConstraint:widthFenceConstraint];
    CGFloat fittingHeight = [templateHeaderFooterView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;
    [templateHeaderFooterView removeConstraint:widthFenceConstraint];
    
    if (fittingHeight == 0) {
        fittingHeight = [templateHeaderFooterView sizeThatFits:CGSizeMake(CGRectGetWidth(self.frame), 0)].height;
    }
    
    return fittingHeight;
}

@end

@implementation UITableViewCell (FDTemplateLayoutCell)

- (BOOL)fd_isTemplateLayoutCell {
    return [objc_getAssociatedObject(self, _cmd) boolValue];
}

- (void)setFd_isTemplateLayoutCell:(BOOL)isTemplateLayoutCell {
    objc_setAssociatedObject(self, @selector(fd_isTemplateLayoutCell), @(isTemplateLayoutCell), OBJC_ASSOCIATION_RETAIN);
}

- (BOOL)fd_enforceFrameLayout {
    return [objc_getAssociatedObject(self, _cmd) boolValue];
}

- (void)setFd_enforceFrameLayout:(BOOL)enforceFrameLayout {
    objc_setAssociatedObject(self, @selector(fd_enforceFrameLayout), @(enforceFrameLayout), OBJC_ASSOCIATION_RETAIN);
}

@end