Question

问：我了解如何在请求内返回承诺，但是如何在另一个请求内的 要求中返回新承诺 ？

我的代码：

request({ // --------------request 1------------
    url: request_data.url,
    method: request_data.method,
    form: request_data.data,
    headers: oauth.toHeader(oauth.authorize(request_data, token))
}, function (err, res, body) {
    body = JSON.parse(body);
    var count = 0;
    for (var i = 0; i < body.items.length; i++) {
        if (body.items[i].name.toLowerCase().indexOf(params.name.toLowerCase()) >= 0) {
            ids[count] = body.items[i].id;
            count++;
        }
    }
    return new Promise((resolve, reject) => { 
        request({  **request 2** ------------request 2--------------
            url: request_data2.url,
            method: request_data2.method,
            form: request_data2.data,
            headers: oauth.toHeader(oauth.authorize(request_data2, token))
        }, function (err2, res2, body2) {
            body2 = JSON.parse(body2);
            var counts = 0;
            var ret = {};
            //console.log(ids[0]);
            for (var i = 0; i < body2.items.length; i++) {
                //console.log(body2.items[i].name);
                for (var y = 0; y < body2.items[i].custom_attributes.length; y++) {
                    if (body2.items[i].custom_attributes[y].attribute_code == 'category_ids') {
                        if (ids[0] == body2.items[i].custom_attributes[y].value) {
                            ret[counts] = body2.items[i].name;
                            counts++;
                        }
                    }
                }
            } //------- resolve / reject ----------
            if (err) {
                reject({
                    statusCode: 500,
                    headers: { 'Content-Type': 'application/json' },
                });
            } else {
                resolve({
                    body: JSON.parse(ret),
                })
            }
        });
    });
});

当我只有一个请求时，输出有效。但是，当请求中有另一个请求时，当我尝试调用此函数时，会收到一个空输出{} 。

Answer 1

首先，停止在非承诺回调中执行操作。除了解决承诺外，您不应在“请求内”做任何事情：

function requestAsync(data, headers) {
    return new Promise((resolve, reject) => {
        request({
            url: data.url,
            method: data.method,
            form: data.data,
            headers,
        }, function (err, res, body) {
            if (err) reject(err); // don't ignore errors!
            else resolve(body);
        });
    });
}

现在，您可以将业务代码放入then回调中，并且从then回调中，您还可以return其他承诺来建立一个链：

const oauthHeaders = oauth.toHeader(oauth.authorize(request_data, token);
return requestAsync(request_data, oauthHeaders).then(JSON.parse).then(body => { /*
^^^^^^ */
    const ids = [];
    var count = 0;
    for (var i = 0; i < body.items.length; i++) {
        if (body.items[i].name.toLowerCase().indexOf(params.name.toLowerCase()) >= 0) {
            ids[count] = body.items[i].id;
            count++;
        }
    }
    return requestAsync(request_data2, oauthHeaders).then(JSON.parse).then(body2 => {
//  ^^^^^^
        var counts = 0;
        var ret = {};
        //console.log(ids[0]);
        for (var i = 0; i < body2.items.length; i++) {
            //console.log(body2.items[i].name);
            for (var y = 0; y < body2.items[i].custom_attributes.length; y++) {
                if (body2.items[i].custom_attributes[y].attribute_code == 'category_ids') {
                    if (ids[0] == body2.items[i].custom_attributes[y].value) {
                        ret[counts] = body2.items[i].name;
                        counts++;
                    }
                }
            }
        }
        return {
//      ^^^^^^
            body: JSON.stringify(ret), // I don't think you meant `parse` here
        };
    });
}).catch(err => {
    return { // I don't think you want to `throw` this object
        statusCode: 500,
        headers: { 'Content-Type': 'application/json' },
    };
});

如何在另一个请求中返回一个承诺请求？

1 个答案: