类型错误：无法读取算法交易中未定义的属性'then'

Question

由于某种原因，每次运行此代码时，我都会捕获"TypeError:无法读取未定义的"的属性"then"；错误我不明白为什么。这是代码：

console.log("BUY");
exchange.marketBuy()
.then(res => {
console.log("Buy successful");
hasPosition = true
setTimeout(strategy, 1000)
})
.catch(console.error);

marketBuy((函数是

marketBuy() {
client.getLatestInformation()
.then(response => {
var price = response.result[0].last_price;
client.placeActiveOrder({
side: "Buy",
symbol: "BTCUSD",
order_type: "Market",
qty: 20,
time_in_force: "GoodTillCancel",
take_profit: price * 1.5,
stop_loss: price / 1.5})
.then(response => console.log(response))
})

我试过

console.log("BUY");
exchange.marketBuy()
.then(res => {
hasPosition = true
setTimeout(strategy, 1000)
return Promise.resolve(console.log("Buy successful"));
})
.catch(console.error);

我似乎找不到问题所在。有什么想法吗？

Answer 1

您有几个不同的问题。正如其他人已经指出的那样，您不会从makeBuy()方法返回promise。但是，它似乎并不像建议的那样简单地添加一个return语句那么容易。这是因为在将hasPosition设置为true之前，您实际上需要等待内部promise从client.placeActiveOrder()解析。

所以你有两个选择(推荐#2(：

1. 将必须等待内部promise解决的代码移动到内部promise的.then()(这会在hasPosition变量中产生自己的问题(：

client.placeActiveOrder({
side: "Buy",
symbol: "BTCUSD",
order_type: "Market",
qty: 20,
time_in_force: "GoodTillCancel",
take_profit: price * 1.5,
stop_loss: price / 1.5})
.then(response => {
console.log(response);
console.log("Buy successful");
hasPosition = true;
setTimeout(strategy, 1000);
});

2. 使用async/await使代码读起来像工作流：

async marketBuy() {
const response = await client.getLatestInformation();
const price = response.result[0].last_price;
const order = await client.placeActiveOrder({
side: "Buy",
symbol: "BTCUSD",
order_type: "Market",
qty: 20,
time_in_force: "GoodTillCancel",
take_profit: price * 1.5,
stop_loss: price / 1.5
})
return order;
}

建议选择二，因为它允许您按照预期的方式进行编码。以下是不再抛出错误的调用代码：

console.log("BUY");
exchange.marketBuy()
.then(res => { // res here is the order returned
console.log("Buy successful");
hasPosition = true
setTimeout(strategy, 1000)
})
.catch(console.error);