如何检查一条记录是否在 2 个不同的表上？

Question

我正在使用 Parse.com 并寻找一种有效的方法来处理这个问题。

我有一个 Sales table，它有一个 User 参考列和一个 Offer 参考列。

销售 table 跟踪哪些用户前来领取优惠（即 10% 的折扣）。

所以我有以下子类

Offers
Users
Sales

我想显示所有可用的优惠，但设置了一个本地 hasBeenUsed 标志，这样我可以在优惠已经被使用时以不同的方式显示它们。

目前我可以创建可用优惠的本地数组，但我不确定如何相应地设置此 hasBeenUsed 标志。

var query = Message.query()
query.findObjectsInBackgroundWithBlock { (objects: [AnyObject]!, error: NSError!) -> Void in
 for object in objects {
  var offer = Offer()
  offer.info = object["info"] as String
  if (also on the Sales list)
   offer.hasBeenUsed = true
  }
  self.offers.insert(offer, atIndex: 0)
 }
}

Answer 1

警告：请原谅我犯的任何 Swift 错误。我还在写Objective-C，我已经尽力写好Swift，但我还不是语法专家

我能想到的最佳答案是您需要 2 个查询（假设您关心 Sales 用于 [PFUser currentUser] 或 PFUser.currentUser()）：

获取当前用户的 Sales 个对象列表
获取所有（当前）Offer 个对象的列表。

查询 1

Swift版本

var query = PFQuery(className:"Sales")
query.includeKey("Offer")
query.whereKey("User", equalTo:PFUser.currentUser())
query.findObjectsInBackgroundWithBlock { (objects: [AnyObject]!, error: NSError!) -> Void in
    if error == nil {
        // Assign the objects to a property or something
        self.sales = objects
        // **Then**, run query 2
        runQuery2()

    } else {
        // Do error handling...
    }
}

Objective-C版本

PFQuery *query = [PFQuery queryWithClassName:@"Sales"];
[query includeKey:@"Offer"];
[query whereKey:@"User" equalTo:[PFUser currentUser]];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    if (error != nil) {
        // Do error handling

    } else {
        // Assign the objects to a property or something...
        self.sales = objects;
        // **Then**, run query 2
        [self runQuery2];

    }
}
 ];

查询 2

Swift版本

var query = PFQuery(className:"Offers")
// Whatever query constraints you need to get "current" offers
query.findObjectsInBackgroundWithBlock { (objects: [AnyObject]!, error: NSError!) -> Void in
    if error == nil {
        // Assign the objects to a property or something
        self.offers = objects;
        // At this point, you have all the data you need, so call the "filter" method
        filter()

    } else {
        // Do error handling...
    }
}

Objective-C版本

PFQuery *query = [PFQuery queryWithClassName:@"Offers"];
// Whatever query constraints you need to get "current" offers
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    if (error != nil) {
        // Do error handling

    } else {
        // Assign the objects to a property or something
        self.offers = objects;
        // At this point, you have all the data you need, so call the "filter" method
        [self filter];

    }

}
 ];

过滤方法

这假定了 2 个属性："sales"，当前用户的销售数组，以及 "offers"，所有当前优惠的数组

Swift版本

// First, get all of the "redeemed" offers into an array
var localOffers = [PFObject]()
for sale in self.sales {
    localOffers.append(sale.offer)
    // It might be easier to do it this way
    // localOffers.append(sale.offer.objectId)
}

// Next, iterate the "all offers" array and mark each offer as redeemed/not redeemed
for offer in self.offers {
    if (localOffers.containsObject(offer)) {
    // Alternative check
    // if (localOffers.containsObject(offer.objectId)) {
        offer.hasBeenUsed = true
    } else {
        offer.hasBeenUser = false
    }
}

Objective-C版本

// First, get all of the "redeemed" offers into an array
NSMutableArray *localOffers = [NSMutableArray array];
for (PFObject *sale in self.sales) {
    [localOffers addObject:sale.offer];
    // It might be easier to do it this way
    // [localOffers addObject:self.offer.objectId];
}

// Next, iterate the "all offers" array and mark each offer as redeemed/not redeemed
for (PFObject *offer in self.offers) {
    if ([localOffers containsObject:offer]) {
    // Alternative check
    // if ([localOffers containsObject:offer.objectId]) {
        offer[@"hasBeenUsed"] = @(YES);
    } else {
        offer[@"hasBeenUsed"] = @(NO);
    }
}

至此，您已获得根据优惠是否已兑换以不同方式显示数据所需的内容。请注意不要将 hasBeenUsed 值保存到 Parse ，除非那是你想要的。

如何检查一条记录是否在 2 个不同的表上？

How to check if a record is on 2 different tables?

swift

parse-platform

查询 1

Swift版本

Objective-C版本

查询 2

Swift版本

Objective-C版本

过滤方法

Swift版本

Objective-C版本