Question

可以将承诺错误解决为高阶承诺吗 EX

#include <stdio.h> 
#include <iostream> 
#include <string> 
using namespace std;

template <typename T,typename U>
class KeyValuePair {

public:
    KeyValuePair(T key, T value)
    : _key{key}, _value{value} {}

    T key() const {
        return _key;
    }
    T value() const {
        return _value;
    }
    string string(T key) {
        return key.to_string();
    }
private:
    T _key;
    T _value;
};

template <typename T, typename U>
ostream& operator<<(ostream& out, const KeyValuePair<T, U>& pair)
{
    out << "{" << pair.key() << ":" << pair.value() << "}";
    return out;
}

int main() {
    KeyValuePair<int, bool> kvp1{ 1, true };
    KeyValuePair<string, int> kvp2{ string("count"), 7 };
    cout << "KVP1 = " << kvp1 << endl;
    cout << "KVP2 = " << kvp2 << endl;
}

get_data_from_db可以调用其他异步函数。拒绝并没有使错误返回更高的承诺

Answer 1

由于await也适用于非承诺，因此您可以保存整个Promise构造：

const async_function = () => get_data_from_db(); 

(async()=>{
    try {
        //call async function
        const data = await async_function();
        console.log(data);

    } catch (err) {
        console.error(err.message);
    }
})();

Answer 2

可以兑现诺言

有时候还可以。将被拒绝的承诺视为“异步抛出”，并对其进行捕获

但是您的代码是反模式http://bluebirdjs.com/docs/anti-patterns.html#the-explicit-construction-anti-pattern

的示例

const async_function = async (resolve, reject) => {
  // some code 
  get_data_from_db
     .then(data => resolve(null,data))
     .catch(e => resolve(e, null)
}

您可以将其重写为：

const async_function = () =>
  get_data_from_db()
     .catch(e => e) // it will be resolved with e

将承诺错误解决为高阶承诺可以吗

2 个答案: