向子类PFObject添加NSArray属性

Question

我有两个子类PFObjects，如下所示：

@interface BQQuestion : PFObject<PFSubclassing>

@property (retain) NSString *user;
@property (retain) NSString *questionText;
@property (retain) NSArray *answers; //this is intended to hold an array of BQAnswers 

+ (NSString *)parseClassName;

@end


@interface BQAnswer : PFObject<PFSubclassing>

@property (retain) NSString *user;
@property (retain) BQQuestion *question;
@property (retain) NSString *answerText;
@property int votes;

+(NSString *)parseClassName;

@end

我正在尝试使用以下代码将BQAnswers添加到property的answers属性中：

    BQQuestion *t = [BQQuestion object];
    t.questionText = @"Another test";
    BQAnswer *one = [BQAnswer object];
    one.answerText = @"Very nice.";
    BQAnswer *two = [BQAnswer object];
    two.answerText = @"Good.";

    t.answers = @[one, two];

    [t saveInBackground];

1和2都保存到解析云中，但是没有为BQQuestion.answers生成任何列，因此不保存关联。我在这里搞错了什么？

任何帮助都将不胜感激。谢谢!

Answer 1

指向PFObjects数组的指针是一个PFRelation。为此，您需要在object对象中创建一个列，其中包含一个指向Answer对象的关系。我假设您在parse中的类称为“问题”，添加的包含指向答案的关系的列称为“答案”。

BQQuestion *question = [PFObject objectWithClassName:@"Question"];
PFRelation *answers = [t relationForKey:@"answers"];
for (PFObject *answer in answers) {
  [question add:answer];
}
[question saveInBackground];

要检索答案对象，请执行以下操作：

BQQuestion *question = //assume you have the question object;
PFRelation *answers = [question relationForKey:@"answers"];
PFQuery *query = [answers query];
[query findObjectsInBackgroundWithBlock:^(NSArray *results, NSError *error) {
    // results contains all the answers to that question
}];