iOS TableViewCell中的KVO的使用

#import "MessageCell.h"

@implementation MessageCell

- (void)awakeFromNib {
    [super awakeFromNib];
    // Initialization code

    self.bradgeView.layer.masksToBounds = YES;
    self.bradgeView.layer.cornerRadius = 5;
}

- (void)setSelected:(BOOL)selected animated:(BOOL)animated {
    [super setSelected:selected animated:animated];

    // Configure the view for the selected state
}

- (void)setMsgModel:(MessageModel *)msgModel{
    _msgModel = msgModel;
    self.msgLbl.text = msgModel.msgTitle;
    if ([msgModel.isRead integerValue] == 1) {
        self.bradgeView.hidden = YES;
    }else{
         self.bradgeView.hidden = NO;
    }
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context{
    if ([keyPath isEqualToString:@"isRead"] && [object isKindOfClass:[MessageModel class]]) {
        
        if ([self.msgModel.isRead integerValue] == 1) {
            _bradgeView.hidden = YES;
        }
    }
}

- (void)tableView:(UITableView *)tableView willDisplayCell:(nonnull UITableViewCell *)cell forRowAtIndexPath:(nonnull NSIndexPath *)indexPath{
    if (_msgDataArr.count > indexPath.row) {
         MessageModel *msgModel = _msgDataArr[indexPath.row];
        [msgModel addObserver:cell forKeyPath:@"isRead" options:NSKeyValueObservingOptionNew context:nil];
    }
}

- (void)tableView:(UITableView *)tableView didEndDisplayingCell:(nonnull UITableViewCell *)cell forRowAtIndexPath:(nonnull NSIndexPath *)indexPath{
     if (_msgDataArr.count > indexPath.row) {
          MessageModel *msgModel = _msgDataArr[indexPath.row];
         [msgModel removeObserver:cell forKeyPath:@"isRead"];
     }
 }

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
    MessageModel *msgModel = _msgDataArr[indexPath.row];
    if ([msgModel.isRead integerValue] != 1) {
        msgModel.isRead = @"1";
    }
    
}