動態計算tablviewcell高度

根據實體類的屬性，計算出要顯示的高度，然後設定tableview代理

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    THDiaryEntry *entry = [self.fetchedResultsController objectAtIndexPath:indexPath];
    return [THEntryCell heightForEntry:entry];
}

THEntryCell.m :

+ (CGFloat)heightForEntry:(THDiaryEntry *)entry {
    const CGFloat topMargin = 35.0f;
    const CGFloat bottomMargin = 80.0f;
    const CGFloat minHeight = 106.0f;

    UIFont *font = [UIFont systemFontOfSize:[UIFont systemFontSize]];

    CGRect boundingBox = [entry.body boundingRectWithSize:CGSizeMake(202, CGFLOAT_MAX) options:(NSStringDrawingUsesFontLeading|NSStringDrawingUsesLineFragmentOrigin) attributes:@{NSFontAttributeName: font} context:nil];

    return MAX(minHeight, CGRectGetHeight(boundingBox) + topMargin + bottomMargin);
}

注，cellForRowAtIndexPath方法裡最好不要太多的程式碼，把能抽取的程式碼都抽出來，比如設定屬性以及顯示在cell子類設定，看起來就清晰簡潔的多了

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    THEntryCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

    THDiaryEntry *entry = [self.fetchedResultsController objectAtIndexPath:indexPath];
    [cell configureCellForEntry:entry];

    return cell;
}

THEntryCell.m:

- (void)configureCellForEntry:(THDiaryEntry *)entry {
    self.bodyLabel.text = entry.body;
    self.locationLabel.text = entry.location;

    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"EEEE, MMMM d yyyy"];
    NSDate *date = [NSDate dateWithTimeIntervalSince1970:entry.date];

    self.dateLabel.text = [dateFormatter stringFromDate:date];

    if (entry.imageData) {
        self.mainImageView.image = [UIImage imageWithData:entry.imageData];
    } else {
        self.mainImageView.image = [UIImage imageNamed:@"icn_noimage"];
    }

    if (entry.mood == THDiaryEntryMoodGood) {
        self.moodImageView.image = [UIImage imageNamed:@"icn_happy"];
    } else if (entry.mood == THDiaryEntryMoodAverage) {
        self.moodImageView.image = [UIImage imageNamed:@"icn_average"];
    } else if (entry.mood == THDiaryEntryMoodBad) {
        self.moodImageView.image = [UIImage imageNamed:@"icn_bad"];
    }

    self.mainImageView.layer.cornerRadius = CGRectGetWidth(self.mainImageView.frame) / 2.0f;

    if (entry.location.length > 0) {
        self.locationLabel.text = entry.location;
    } else {
        self.locationLabel.text = @"No location";
    }
}