我有一个返回对象数组时失败的方法。如标题中所述 - 确认数组已填充但响应中为空。
以下是完整的流程：
网址：
http://localhost:53000/api/v1/landmarks?lat=40.76959&lng=-73.95136&radius=160
路由到相应的索引：
api.route('/api/v1/landmarks').get(Landmark.list);
索引呼叫服务：
exports.list = (req, res) => {
const landmark = new LandmarkService();
landmark.getLandmarks(req)
.then(landmarks => {
var response = new Object();
response.startindex = req.query.page;
response.limit = req.query.per_page;
response.landmarks = landmarks;
res.json(response);
})
.catch(err => {
logger.error(err);
res.status(422).send(err.errors);
});
};
服务方法使用数据访问类返回承诺
getLandmarks(req) {
const params = req.params || {};
const query = req.query || {};
const page = parseInt(query.page, 10) || 1;
const perPage = parseInt(query.per_page, 10);
const userLatitude = parseFloat(query.lat);
const userLongitude = parseFloat(query.lng);
const userRadius = parseFloat(query.radius) || 10;
const utils = new Utils();
const data = new DataService();
const landmarkProperties = ['key','building','street','category','closing',
'email','name','opening','phone','postal','timestamp','type','web'];
return data.db_GetAllByLocation(landmarksRef, landmarkLocationsRef,
landmarkProperties, userLatitude, userLongitude, userRadius);
} // getLandmarks
但是，响应始终为空。
我在被调用的方法中构建一个数组，并用JSON对象填充它。这就是应该在回复中发回的内容。在命中return语句之前，我可以确认属性数组是否已正确填充。我可以将它记录到控制台。我也可以成功发回一个填充了存根值的测试数组。
我有一种感觉，我是如何在Promise中设置的？
应该返回对象数组的数据访问方法：
db_GetAllByLocation(ref, ref_locations, properties, user_latitude, user_longitude, user_radius)
{
const landmarkGeoFire = new GeoFire(ref_locations);
var geoQuery = landmarkGeoFire.query({
center: [user_latitude, user_longitude],
radius: user_radius
});
var locations = [];
var onKeyEnteredRegistration = geoQuery.on("key_entered", function (key, coordinates, distance) {
var location = {};
location.key = key;
location.latitude = coordinates[0];
location.longitude = coordinates[1];
location.distance = distance;
locations.push(location);
});
var attributes = [];
var onReadyRegistration = geoQuery.on("ready", function() {
ref.on('value', function (refsSnap) {
refsSnap.forEach((refSnap) => {
var list = refSnap;
locations.forEach(function(locationSnap)
{
//console.log(refSnap.key, '==', locationSnap.key);
if (refSnap.key == locationSnap.key)
{
var attribute = {};
for(var i=0; i<=properties.length-1; i++)
{
if(properties[i] == 'key') {
attribute[properties[i]] = refSnap.key;
continue;
}
attribute[properties[i]] = list.child(properties[i]).val();
}
attribute['latitude'] = locationSnap.latitude;
attribute['longitude'] = locationSnap.longitude;
attribute['distance'] = locationSnap.distance;
attributes.push(attribute);
} // refSnap.key == locationSnap.key
}); // locations.forEach
}); // refsSnap.forEach
return Promise.resolve(attributes); <-- does not resolve (throws 'cannot read property .then')
//geoQuery.cancel();
}); // ref.on
}); // onreadyregistration
return Promise.resolve(attributes); <-- comes back empty
}
答案 0 :(得分：0)
似乎data.db_GetAllByLocation是一个异步函数，因此调用解析（landmarks）;在执行异步函数完成之前调用。如果data.db_GetAllByLocation返回一个promise，则调用promise中的resolve（landmarks）。
data.db_GetAllByLocation().then(function() {
resolve();
})
还尝试以下修改过的db_GetAllByLocation（）
db_GetAllByLocation(ref, ref_locations, properties, user_latitude, user_longitude, user_radius)
{
return new Promise(function(resolve, reject){
const landmarkGeoFire = new GeoFire(ref_locations);
var geoQuery = landmarkGeoFire.query({
center: [user_latitude, user_longitude],
radius: user_radius
});
var locations = [{}];
var onKeyEnteredRegistration = geoQuery.on("key_entered", function (key, coordinates, distance) {
var location = {};
location.key = key;
location.latitude = coordinates[0];
location.longitude = coordinates[1];
location.distance = distance;
locations.push(location);
});
var attributes = [{}];
var onReadyRegistration = geoQuery.on("ready", function() {
ref.on('value', function (refsSnap) {
refsSnap.forEach((refSnap) => {
var list = refSnap;
locations.forEach(function(locationSnap)
{
if (refSnap.key == locationSnap.key)
{
var attribute = {};
for(var i=0; i<=properties.length-1; i++)
{
if(properties[i] == 'key') {
attribute[properties[i]] = refSnap.key;
continue;
}
attribute[properties[i]] = list.child(properties[i]).val();
}
attribute['latitude'] = locationSnap.latitude;
attribute['longitude'] = locationSnap.longitude;
attribute['distance'] = locationSnap.distance;
attributes.push(attribute);
} // refSnap.key == locationSnap.key
}); // locations.forEach
}); // refsSnap.forEach
// return JSON.stringify(attributes);
return resolve(attributes);
}); // ref.on
}); // onreadyregistration
});
}
答案 1 :(得分：0)
好的，我通过删除所有代码并编写一些测试逻辑来对此进行排序（我应该在发布问题之前完成此操作）。
以下流程对我有用，并且应用回我的代码，给了我正在寻找的结果。无需重新发布代码，但以下流程可能会对某些人有所帮助。
<强>路线
api.route('/api/v1/landmarks').get(Landmark.test);
<强>索引
exports.test = (req, res) => {
const landmark = new LandmarkService();
landmark.getLandmarksTest(req)
.then(landmarks => {
var final = {};
final.attr1 = 'attr1';
final.attr2 = 'attr2';
final.landmarks = landmarks;
res.json(final);
})
.catch(err => {
logger.error(err);
res.status(422).send(err.errors);
});
};
服务方法
getLandmarksTest(req)
{
const data = new DataService();
data.db_PromiseTest().then(results => {
return Promise.resolve(results);
}).catch(err => {
return Promise.reject(err.errors);
});
}
数据层方法
db_PromiseTest()
{
var stub = {
"name": "Madame Uppercut",
"age": 39,
"secretIdentity": "Jane Wilson",
"powers": [
"Million tonne punch",
"Damage resistance",
"Superhuman reflexes"
]
};
return Promise.resolve(stub);
}