Question

我有一个Parse类“Activity”和“Photo”。如何从currentUser获取PFObjects的NSArray喜欢的图像？

PFQuery *queryLikedPhoto = [PFQuery queryWithClassName:@"Activity"];
[queryLikedPhoto whereKey:@"type" equalTo:@"like"];
[queryLikedPhoto whereKey:@"fromUser" equalTo:[PFUser currentUser]];
[queryLikedPhoto includeKey:@"photo"];
[queryLikedPhoto findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    if (!error) {
        for (PFObject *object in objects) {
            PFObject *photoObject = [object objectForKey:@"photo"];
            [photoObject fetchIfNeededInBackgroundWithBlock:^(PFObject *photoObjects, NSError *error) {
                NSLog(@"photoObjects: %@", photoObjects);
            }];
        }
    }
}];

它用图像检索PFOjects，但是如何将它保存到NSArray中以便进一步使用？！（使用NSMutableArray的变体不起作用）：

PhotoObjects: <Photo: 0x166baf30, objectId: Q0H7XKYeCU, localId: (null)> { image = "<PFFile: 0x166ba810>"; thumbnail = "<PFFile: 0x166ba450>"; user = "<PFUser: 0x1668c6f0, objectId: qGYdDnAtbD, localId: (null)>"; username = "Tim"; } 2015-10-18 23:39:57.058 MyApp[5817:572564] photoObjects: <Photo: 0x166bdec0, objectId: eWGonc9YLz, localId: (null)> { image = "<PFFile: 0x166bd9e0>"; thumbnail = "<PFFile: 0x166bd6a0>"; user = "<PFUser: 0x1668c6f0, objectId: qGYdDnAtbD, localId: (null)>"; username = "Steve"; }

此查询看起来更好修改

PFQuery *queryLikedPhoto = [PFQuery queryWithClassName:@"Activity"];
[queryLikedPhoto whereKey:@"type" equalTo:@"like"];
[queryLikedPhoto whereKey:@"fromUser" equalTo:[PFUser currentUser]];
[queryLikedPhoto whereKeyExists:@"photo"];
[queryLikedPhoto findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    if (!error) {
        self.likedPhotoObjects = [NSMutableArray array];
        if (objects.count >0) {
            for (PFObject *object in objects) {
                PFObject *photoObject = [object objectForKey:@"photo"];
                [self.likedPhotoObjects addObject:photoObject];
            }
        }
           [self.collectionView reloadData];
    }
}];

Answer 1

根据您粘贴的打印件判断，查询工作正常。查看有关如何处理PFFiles的指南。到目前为止你所做的就是获取指向文件的指针，所以现在你需要自己下载文件。（It's all in the guide）

Answer 2

从PFQUERY中提取图片

你似乎正在治疗你的＆＃34;照片＆＃34; PFFile对象作为PFObject而不是PFFile。

在查询块中插入以下代码：

PFFile *imageFile = [object objectForKey:@"photo"];

[imageFile getDataInBackgroundWithBlock:^(NSData *data, NSError *error)
{
    if (!error)
    {
        // SUCCESS.

        imageView.image = [UIImage imageWithData:data];                     
    }
    else
    {
        // ERROR.

        NSLog(@"%@", error);
    }
}];

保存图片

我会使用图像缓存Cocoa Pod [即。 SAM CACHE]。

使用SAM缓存时，保存图像文件非常简单：

[[SAMCache sharedCache] setImage:[UIImage imageWithData:data] forKey:imageKey];

其中：imageKey是指附加到数据表中对象的唯一NSString [即。 ObjectId]。

检索出图像

为了将来检索图像文件，我执行以下代码行：

UIImage *cacheImage = [[SAMCache sharedCache] imageForKey:imageKey];

检查图像是否处于缓存状态

检查imageKey缓存中是否存在图像

UIImage *cacheImage = [[SAMCache sharedCache] imageForKey:imageKey];

if ( cacheImage )
{
    // Image exists within cache.
}
else
{
    // Image does not exist within cache.
}

用于缓存的替代方案

Parse.com还提供了SDK中引用的缓存功能。

有关详细信息，请参阅以下链接：

https://www.parse.com/docs/ios/guide#queries-caching-queries

如何从当前用户获取所有喜欢的图像（指针）？

2 个答案: