3

在这里，我们尝试使用 javascript 以功能方式进行大量调用，问题是我们最终得到 Reader.of(Task.of(Reader.of(Task.of)))，所以我们需要映射(map(map(map))) 我们需要操作的值。

计算需要转到 DynamoDB 表，获取特定属性，然后再次转到 DynamoDB 并获取另一个属性，然后转到 facebook api 获取集合，最后将该信息存储在 Dynamo 中的表中。因此，每个调用都使用 AWS javascript 插件和 node.js 中的 facebook Graph 插件。所以我们需要在运行时传递 AWS 依赖，然后我们需要分叉，然后再次传递 AWS 并再次分叉，然后在运行时传递 FBGraph 并再次分叉，如果您正在构建计算，这有点乏味。

无论如何这里是代码：

require('pointfree-fantasy').expose(global)
import Reader from 'fantasy-readers'
import Task from 'data.task'
import _ from 'ramda'


const log = x => {console.log(x); return x}

const ReaderTask = Reader.ReaderT(Task)

// scan :: string -> [a]
const scan = x => Reader.ask.map(env => env.aws.scanAsync({tableName: x}))

// batchGetItems :: [a] -> [b]
const batchGetItem = x => Reader.ask.map(env => env.aws.batchGetItemAsync(x))

// batchWriteItem :: [a] -> [b]
const batchWriteItem = x => Reader.ask.map(env => env.aws.batchWriteItemAsync(x))

// scanCampaigns :: null -> [a]
const scanCampaigns = () => scan('CampaignStats')

const FBBatchGetItem = x => Reader.ask.map(env => env.fb.batchAsync(x))

const getCampaigns = compose(scanCampaigns, Reader.of)

const groupUsers = _.groupBy(x => x.user_fbid)

const batchGetAccessToken = chain(batchGetItem, ReaderTask.of)

const getCampaignsInsights = chain(FBBatchGetItem, ReaderTask.of)

const saveInsights = chain(batchWriteItem, ReaderTask.of)

const updateCampaignStats = chain(batchWriteItem, ReaderTask.of)

const taskOfEvery = (Task, num) => compose(map(Task.of),_.splitEvery(num))

const runTaskWithFn = (fn, task) => fn(task.fork(err => 'err', x => x))

const filterActive = _.filter(x => x.active === 'true')

const getItems = x => x.Items

const groupAndFilter = compose(groupUsers, filterActive, getItems)

// filterByLastFetch :: ([a], string) => [a]
const filterByLastFetch = (x, y) => x.filter(x => x.last_fetch < y)

export {getCampaigns, batchGetAccessToken, getCampaignsInsights, saveInsights,
        groupUsers,filterByLastFetch, updateCampaignStats, taskOfEvery,
        runTaskWithFn, filterActive, groupAndFilter,
        getItems}

目标是只将 AWS 插件和 FBGraph 插件传递给计算一次，构建一个优雅的组合，如：

const computation = compose(saveIntoDynamo3, fetchFromFacebook,fetchFromDynamo2,fetchFromDynamo)

接着：

computation().run({aws: AWSService, FB: FBGraph})

4

0 回答 0