通过 Firebase 在 Swift 中点赞/反对系统 [英] Upvote/Downvote system within Swift via Firebase

问题描述

我已经查看了数小时的代码和注释，但我一直在努力寻找任何文档来帮助我在带有 firebase 的 swift 应用程序中对对象进行投票和投票.

I've looked over hours of code and notes and I'm struggling to find any documentation that would help me with upvoting and downvoting an object in a swift app with firebase.

我有一个照片库，我想为图像添加 Instagram 风格的赞.用户已经使用 firebase auth 登录，所以我有他们的用户 ID.

I have a gallery of photos and I'm looking to add an instagram style upvote to images. The user has already logged with firebase auth so I have their user ID.

我只是在努力弄清楚方法以及需要在 firebase 中设置哪些规则.

I'm just struggling to figure the method and what rules need to be set in firebase.

任何帮助都会很棒.

推荐答案

我将描述我如何在社交网络应用程序中实现这样的功能 Impether 使用 Swift 和 Firebase.

I will describe how I implemented such a feature in social networking app Impether using Swift and Firebase.

因为upvoting 和downvoting 是类似的，所以我只会描述upvoting.

Since upvoting and downvoting is analogous, I will describe upvoting only.

总体思路是直接在与计数器相关的图像数据对应的节点中存储一个 upvotes 计数器，并使用事务写入更新计数器值，以避免数据不一致.

例如，假设您在路径 /images/$imageId/ 中存储单个图像数据，其中 $imageId 是用于标识特定图像 - 例如可以通过函数 childByAutoId 包含在适用于 iOS 的 Firebase 中.然后在该节点对应于单张照片的对象看起来像:

For example, let's assume that you store a single image data at path /images/$imageId/, where $imageId is an unique id used to identify a particular image - it can be generated for example by a function childByAutoId included in Firebase for iOS. Then an object corresponding to a single photo at that node looks like:

$imageId: {
   'url': 'http://static.example.com/images/$imageId.jpg',
   'caption': 'Some caption',
   'author_username': 'foobarbaz'
}

我们想要做的是给这个节点添加一个upvote counter，这样就变成了:

What we want to do is to add an upvote counter to this node, so it becomes:

$imageId: {
   'url': 'http://static.example.com/images/$imageId.jpg',
   'caption': 'Some caption',
   'author_username': 'foobarbaz',
   'upvotes': 12,
}

当您创建一个新图像时(可能是当用户上传它时)，那么您可能需要使用 0 或其他一些常量来初始化 upvote 计数器值，具体取决于您想要实现的目标.

When you are creating a new image (probably when an user uploads it), then you may want to initialize the upvote counter value with 0 or some other constant depending on what are you want to achieve.

在更新特定的 upvotes 计数器时，您希望使用事务以避免其值不一致(当多个客户端想要同时更新计数器时可能会发生这种情况).

When it comes to updating a particular upvotes counter, you want to use transactions in order to avoid inconsistencies in its value (this can occur when multiple clients want to update a counter at the same time).

幸运的是，在 Firebase 和 Swift 中处理事务写入非常简单:

Fortunately, handling transactional writes in Firebase and Swift is super easy:

func upvote(imageId: String,
            success successBlock: (Int) -> Void,
            error errorBlock: () -> Void) {

    let ref = Firebase(url: "https://YOUR-FIREBASE-URL.firebaseio.com/images")
        .childByAppendingPath(imageId)
        .childByAppendingPath("upvotes")

    ref.runTransactionBlock({
        (currentData: FMutableData!) in

        //value of the counter before an update
        var value = currentData.value as? Int

        //checking for nil data is very important when using
        //transactional writes
        if value == nil {
            value = 0
        }

        //actual update
        currentData.value = value! + 1
        return FTransactionResult.successWithValue(currentData)
        }, andCompletionBlock: {
            error, commited, snap in

            //if the transaction was commited, i.e. the data
            //under snap variable has the value of the counter after
            //updates are done
            if commited {
                let upvotes = snap.value as! Int
                //call success callback function if you want
                successBlock(upvotes)
            } else {
                //call error callback function if you want
                errorBlock()
            }
    })
}

上面截取的代码实际上几乎就是我们在生产中使用的代码.希望对你有帮助:)

The above snipped is actually almost exactly the code we use in production. I hope it helps you :)

这篇关于通过 Firebase 在 Swift 中点赞/反对系统的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！