javascript - Promise Chain 在第一个 Promise 返回时退出

Question

我有以下缓存存储:

const BPromise = require('bluebird');

const LRU = require('lru-cache');
const product_cache = new LRU(5000);

function getCache(cacheName) {
    switch (cacheName) {
        case 'product_cache':
            return BPromise.resolve(product_cache);
        default:
            return BPromise.resolve(new LRU(5000));
    }
}

function set(id, uuid, cacheName) {
    return getCache(cacheName).then(function(cache) {
        return BPromise.resolve(cache.set(id,uuid));
    });
}

function get(id, cacheName) {
    return getCache(cacheName).then(function(cache) {
        return BPromise.resolve(cache.get(id));
    });
}

module.exports = {
    set: set,
    get: get,

};

我这样调用它:

    let p = new BPromise(function(resolve, reject){

        if (use_cache) {
            return resolve(id_to_uuid_cache.get(id, cacheName));
        } else {
            return resolve(null);
        }
    });
    let uuid = p;
    if (uuid) {
        result.set(id, uuid);
    } else {
        unknown_ids.push(id);
    }

但是，当 Promise 进入调用 id_to_uuid_cache.get(id, cacheName) 时，它会进入内部 Promise 链

返回 getCache(cacheName).then(function(cache) {
返回 BPromise.resolve(cache.get(id));
});

但是一旦到达终点线:

返回 BPromise.resolve(product_cache);

它跳出了 Promise 行 let uuid = p;
我怎样才能确保在转向 promise 之前完成 promise 链。

Answer 1

由于您的底层代码不是异步的，您甚至根本不应该使用 Promise:

const LRU = require('lru-cache');
const product_cache = new LRU(5000);

function getCache(cacheName) {
    switch (cacheName) {
    case 'product_cache':
        return product_cache;
    default:
        return new LRU(5000);
    }
}

function set(id, uuid, cacheName) {
    const cache = getCache(cacheName);
    return cache.set(id, uuid);
}

function get(id, cacheName) {
    const cache = getCache(cacheName);
    return cache.get(id);
}

module.exports = { set, get };

然后按如下方式调用:

const uuid = use_cache ? id_to_uuid_cache.get(id, cacheName) : null;

if (uuid) {
    result.set(id, uuid);
} else {
    unknown_ids.push(id);
}