使用ramda处理的承诺，并等待

Question

我有一段代码写的lodash象下面这样：

const profit = 
    price - 
    _.sumBy(
    await Promise.all(
     map(uOrder => uOrder.invoice, await order.upstreamOrders), 
    ), 
    'amount', 
); 

我想改变它ramda，后夫妇的思考和阅读一些文件我写下面的代码：

const resualt = R.compose(
    R.pick(['amount']), 
    await Promise.all(), 
    R.map(await order.upstreamOrders, uOrder.invoice), 
); 

当然

其错误和不工作，但它的第一种方法，我想知道如何处理这样的使用ramda完美和功能方式的情况。我该如何执行此操作？ 还下令对象是下面的示例的数组：

{ 
"_id" : ObjectId("59dce1f92d57920d3e62bdbc"), 
"updatedAt" : ISODate("2017-10-10T15:06:34.111+0000"), 
"createdAt" : ISODate("2017-10-10T15:06:33.996+0000"), 
"_customer" : ObjectId("59dce1f92d57920d3e62bd44"), 
"_distributor" : ObjectId("59dce1f92d57920d3e62bd39"), 
"status" : "NEW", 
"cart" : [ 
    { 
     "count" : NumberInt(1), 
     "_item" : ObjectId("59dce1f92d57920d3e62bd57"), 
     "_id" : ObjectId("59dce1f92d57920d3e62bdc1") 
    }, 
    { 
     "count" : NumberInt(1), 
     "_item" : ObjectId("59dce1f92d57920d3e62bd5c"), 
     "_id" : ObjectId("59dce1f92d57920d3e62bdc0") 
    }, 
    { 
     "count" : NumberInt(1), 
     "_item" : ObjectId("59dce1f92d57920d3e62bd61"), 
     "_id" : ObjectId("59dce1f92d57920d3e62bdbf") 
    }, 
    { 
     "count" : NumberInt(1), 
     "_item" : ObjectId("59dce1f92d57920d3e62bd66"), 
     "_id" : ObjectId("59dce1f92d57920d3e62bdbe") 
    }, 
    { 
     "count" : NumberInt(1), 
     "_item" : ObjectId("59dce1f92d57920d3e62bd6b"), 
     "_id" : ObjectId("59dce1f92d57920d3e62bdbd") 
    } 
], 
"_upstreamOrders" : [ 
    "4545643499" 
], 
"key" : "4592846350", 
"__v" : NumberInt(1), 
"_invoice" : "0811260909610702" 

}

Answer 1

我觉得这是一个好的开始打破究竟原始功能是做

const profit = 
    price - // subtract the result 
    _.sumBy(
    await Promise.all(
     // Wait for upstreamOrders to resolve, and grab the 'invoice' 
     // key for each 
     map(uOrder => uOrder.invoice, await order.upstreamOrders), 
    ), 
    // calculate the sum of the invoices, based on the 'amount' key 
    'amount', 
); 

随着该记住我们可以分解这些步骤，并将计算（同步）与数据分开（异步）

Ramda没有sumBy，因为我们可以从其他函数中构建它。如果你打破它，我们所做的就是抢invoice，并在两个不同的地方amount，但我们可以只抓数量的阵列

map(path(['invoice', 'amount'])) 

我们可以丢弃旁边一个sum和subtract创建一个函数，它是从我们的异步代码完全独立

const calculateProfits = (price, orders) => compose(
    subtract(price), 
    sum, 
    map(path(['invoice', 'amount'])), 
)(orders) 

允许我们做一些事情，如：

const profit = calculateProfits(price, await order.upstreamOrders) 

或者，如果calculateProfits是咖喱（我不知道upstreamOrders是如何工作的，难道是返回一个承诺一个getter？）

const getUpstreamOrders = order => order.upstreamOrders 

getUpstreamOrders(order) 
    .then(calculateProfits(price)) 
    .then(profits => { 
    // Do what you want with the profits 
    }) 

最后，在初步尝试

const result = R.compose(
    R.pick(['amount']), 

    // Promise.all is being called without any arguments 
    // it doesn't really fit within `compose` anyway, but if we were 
    // feeding an array of promises through, we'd want to just 
    // put `Promise.all,` 
    await Promise.all(), 

    // the arguments here should be the other way around, we're 
    // mapping over upstreamOrders, and the data comes last 
    // uOrder isn't available in this scope, previously it was 
    // `uOrder => uOrder.invoice`, 
    // invoking a function and returning the invoice for that order 
    R.map(await order.upstreamOrders, uOrder.invoice), 
);