_NSDate 长度无法识别的选择器发送到实例

Question

我正在尝试将 NSString 转换为 NSDate

NSString destructString 是 2015-01-04 08:36:42 +0000

我知道问题从我在下面评论的地方开始，但我似乎找不到问题所在。

程序在该点停止并给出标题中的错误。

代码的重点是比较两个日期以查看哪个日期更早。

PFQuery *query = [PFQuery queryWithClassName:self.parseClassName];


NSDate *today = [[NSDate alloc]init];



[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    if(!error){
    for(PFObject* object in [self objects]){
        NSLog(@"OBJECT:  %@", object);
        PAWPost *post = [[PAWPost alloc] initWithPFObject:object];
        NSLog(@"post: %@", post);
        NSLog(@"today: %@", today);

        NSString *destructString = [post.object objectForKey:selfDestructDateKey];
            NSLog(@"destruct string: %@", destructString);

        NSDateFormatter *dateFormat = [[NSDateFormatter alloc]init];

        [dateFormat setDateFormat:@"yyyy-MM-dd HH:mm:ss zz"];

        //SOURCE OF PROBLEM BEGINS HERE
        NSDate *destructDate = [dateFormat dateFromString:destructString];

        NSLog(@"destruct date: %@", destructDate);

        if([destructDate compare:today] == NSOrderedDescending){
            [object deleteEventually];
            NSLog(@"DESCENDING");
        }

        else
            NSLog(@"NOT DESCENDING");

    }

    }else {

        NSLog(@"Error in findObjectsInBackgroundWithBlock for destruct purposes");
    }
}];

另外我知道关于这个问题还有另一个 post 但是我已经尝试了那个修复（重做格式）但它没有解决问题。提前致谢！

Answer 1

如果对象的类型可能会有所不同，您应该像我添加到您的代码中一样添加类型检查

[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    if(!error){
    for(PFObject* object in [self objects]){
        NSLog(@"OBJECT:  %@", object);
        PAWPost *post = [[PAWPost alloc] initWithPFObject:object];
        NSLog(@"post: %@", post);
        NSLog(@"today: %@", today);

        id destructString = [post.object objectForKey:selfDestructDateKey];
            NSLog(@"destruct string: %@", destructString);
     if ([destructString isKindOfClass:[NSDate class]]) { // already date 
           NSDate * destructDate = (NSDate *)destructString;
     } else { // parse string  
        NSDateFormatter *dateFormat = [[NSDateFormatter alloc]init];

        [dateFormat setDateFormat:@"yyyy-MM-dd HH:mm:ss zz"];

        //SOURCE OF PROBLEM BEGINS HERE
        NSDate *destructDate = [dateFormat dateFromString:destructString];

        NSLog(@"destruct date: %@", destructDate);

        if([destructDate compare:today] == NSOrderedDescending){
            [object deleteEventually];
            NSLog(@"DESCENDING");
        }

        else
            NSLog(@"NOT DESCENDING");
}
    }

    }else {

        NSLog(@"Error in findObjectsInBackgroundWithBlock for destruct purposes");
    }
}];

_NSDate 长度无法识别的选择器发送到实例

_NSDate length unrecognized selector sent to instance

objective-c

nsdate

nsstring

ios