I'm right now working on a web API with expressjs, kotlin and PostgreSQL. I organized my project in an object oriented way. I also created a class for the database that makes all frequently called queries available as a function. Example:
fun addUser(firstName: String, lastName: String, password: String, classId: Int){
client.query("INSERT INTO users(first_name, last_name, password, class_id) values($1, $2, $3, $4)", arrayOf(firstName, lastName, password, classId));
}
This doesn't work however when I'm trying to issue a SELECT query and return the dataset to the function caller since queries are asynchronous. I already tried assigning the result to an attribute of the database object and using it as soon as the value is assigned, but it seems that the value can't be assigned when I'm checking its value permanently. Does anyone know how I could return the value to the function caller?
Thanks in advance for your answers.
Assuming you are using nodejs and the pg module.
As you said since query function is async you cannot return the result to the caller directly. Traditionally in nodejs the caller passes a callback function to handle the result or the error if there is one.
In Kotlin this would look like:
client.query(MY_QUERY_TEMPLATE, params) { err, result ->
if (err != null) {
// do something with the error
} else {
// do something with the result
}
}
To make this a bit neater you could put your result handler in its own function
fun handleResult(err: dynamic, result: dynamic) {
// put your code here
}
And use it like this:
client.query(MY_QUERY_TEMPLATE, params, ::handleResult)
If you don't like this you have another option. The pg library can return Promise. This abstraction allows you to use method chaining like this:
app.get("/promiseStyle") { req, res ->
val params = arrayOf(42) // or something...
fun handleSuccess(result: dynamic) {
for (row in result.rows) {
res.write(row.someField)
}
res.end()
}
fun handleError(error: dynamic) {
res.status(500).send("Something went wrong");
}
client.query(MY_QUERY_TEMPLATE, params)
.then(::handleSuccess)
.catch(::handleError)
}
You may find the following declaration useful for accessing the various pg client functionality:
#JsModule("pg")
external object pg {
class Client {
fun query(query: String, params: Array<Any>): dynamic
fun query(
query: String, params: Array<Any>, cb: (dynamic, dynamic) -> Unit
)
fun connect()
}
}
The postgres client can then be initialized as follows:
val client = pg.Client()
client.connect()
Related
I have
const {data, error, isLoading } = useFetchBulkClassesQuery(something)
to pass data to MySql via this API:
fetchBulkCclasses: builder.query ({
query: (something) => {
return {
url: '/bulkclasses',
params: {
class: something
},
method: 'GET'
at the backend, I have
tyapp.get("/bulkclasses", (req, res) => {
const q = 'select * from recent where ticker in (?)'
db.query(q, [[req.query.ticker]], (err, data) => {
if(err) {return res.json(err)}
return res.json(data)pe here
it al works fine if I use a single variable, like something = 'ClassA'
But I want to use it for multiple entries like ClassA, ClassB, ClassC, ...
But it only takes the first one (or the last one depending on what I try).
What am I doing wrong? Or what haven't I tried (or what do I not know)?
I tries:
Something = ['ClassA', 'ClassB', ...] -> the thing that get passed to the backend is 'ClassA, ClassB' en and it needs to be 'ClassA', 'ClassB', ...
Something = [[ClassA], [ClassB],...] -> same result
It seemed a bit impossible to do, so I did choose the easiest solution: changing the design of my tables and update the query.
I am trying to implement a search function where a user can return other users by passing a username through a component. I followed the ember guides and have the following code to do so in my routes file:
import Ember from 'ember';
export default Ember.Route.extend({
flashMessages: Ember.inject.service(),
actions: {
searchAccount (params) {
// let accounts = this.get('store').peekAll('account');
// let account = accounts.filterBy('user_name', params.userName);
// console.log(account);
this.get('store').peekAll('account')
.then((accounts) => {
return accounts.filterBy('user_name', params.userName);
})
.then((account) => {
console.log(account);
this.get('flashMessages')
.success('account retrieved');
})
.catch(() => {
this.get('flashMessages')
.danger('There was a problem. Please try again.');
});
}
}
});
This code, however, throws me the following error:
"You cannot pass '[object Object]' as id to the store's find method"
I think that this implementation of the .find method is no longer valid, and I need to go about returning the object in a different manner. How would I go about doing this?
You can't do .then for filterBy.
You can't do .then for peekAll. because both will not return the Promise.
Calling asynchronous code and inside the searchAccount and returning the result doesn't make much sense here. since searchAccount will return quickly before completion of async code.
this.get('store').findAll('account',{reload:true}).then((accounts) =>{
if(accounts.findBy('user_name', params.userName)){
// show exists message
} else {
//show does not exist message
}
});
the above code will contact the server, and get all the result and then do findBy for the filtering. so filtering is done in client side. instead of this you can do query,
this.store.query('account', { filter: { user_name: params.userName } }).then(accounts =>{
//you can check with length accounts.length>0
//or you accounts.get('firstObject').get('user_name') === params.userName
//show success message appropriately.
});
DS.Store#find is not a valid method in modern versions of Ember Data. If the users are already in the store, you can peek and filter them:
this.store.peekAll('account').filterBy('user_name', params.userName);
Otherwise, you'll need to use the same approach you used in your earlier question, and query them (assuming your backend supports filtering):
this.store.query('account', { filter: { user_name: params.userName } });
I'm trying to consume a REST webservice, responding with a JSON String containing a fairly "complex" schema.
I created a model that contains every fields sent by the webservice.
Here are the relevant codes that should be a problem :
public getUser(user_id: number): PlanDeCharge.Modeles.User {
var toto;
this.UserRest.get({ user_id: user_id }, function(){}, function(err){
this.$window.location.href = "http://localhost:8080/myapp_webapp/login.do";
}).$promise.then(function(data){
toto = data;
});
return toto;
}
-
this.userConnecte = this.gestionUserService.getUser(759);
-
export function userRest($resource: ng.resource.IResourceService, $cookies: ng.cookies.ICookiesService): PlanDeCharge.Modeles.IUserResource {
this.key = $cookies.get("encodedKey");
var urlService: string = "http://localhost:8080/teambox_webapp/resource-rest/V1_1/users/:user_id";
return <PlanDeCharge.Modeles.IUserResource> $resource(urlService, {user_id: "#user_id"}, {
get:{
headers:{"key" : this.key}
}
});
}
app.factory("UserRest", ["$resource", "$cookies", userRest]);
I did a lot of modifications, trying to fix the call without success... The request actually get a response containing the JSON string, but I can't put it inside an object to be use (like user['id'] = 2)
Thanks in advance
I deleted the last post and made this new one, the first one wasn't clear enough and people were confused
When working with promises you should let Angular handle the resolvement.
Am I right, if you are actually using AngularJS 1 and not ng2 as the question is tagged? The syntax is ng1 anyways.
Some notes on the getUser method. Return the reference created by $resource instead of creating one your self. Further more, use the fat-arrow syntax on the callbacks to bind this to the proper context. See this article for more on this.
To remove even more code use TypeScripts object initialization and init the user id object with just { user_id }. This creates a JavaScript object with a property user_id with the value of user_id.
public getUser(user_id: number): SomeModel {
return this.UserRest
.get({ user_id }, () => { }, () => {
this.$window.location.href = "http://localhost:8080/myapp_webapp/login.do";
});
}
In your component or controller access
this.userConnecte = this.gestionUserService.getUser(759);
Lastly, the factory/service.
Use the fact that $resource is generic and set your variables as constants when not changed.
export function userRest(
$resource: ng.resource.IResourceService,
$cookies: ng.cookies.ICookiesService
): ng.resource.IResourceClass<PlanDeCharge.Modeles.IUserResource> {
this.key = $cookies.get("encodedKey");
const urlService = "http://localhost:8080/teambox_webapp/resource-rest/V1_1/users/:user_id";
return $resource<PlanDeCharge.Modeles.IUserResource>(urlService, { user_id: "#user_id" }, {
get: {
headers: { "key": this.key }
}
});
}
This should fix your problems and make to code more readable. :)
I have a sample code that goes like this:
Client Helper:
getUsername: function (userId) {
Meteor.call("getUsername", userId, function (err, result) {
if(!err) {
Session.set("setUsername", result);
else {
console.log(err);
}
});
return Session.get("setUsername");
}
Server
Meteor.methods({
"getUsername": function (userId) {
var x = Meteor.users.find({_id: userId}, {fields: {username:1}}).fetch()[0];
return x.username;
}
});
The result of this code is an infinite loop of username passing to the client. Is there a way to stop the loop and pass only the data that is needed on the client? I believe the reactivity is causing the data to loop infinitely and I am not sure how to stop it. I tried using "reactive":false on my query in the server but it does not work.
If you want to access username everywhere in client templates (so thats why you put it into session), I would not set it in template helper. I would set it on startup and get username from session in template helpers (without calling server method)
If you need username just in one template, so you want to return its value from your template helper, do not put it into session, just return it in your server method callback.
Based on your sample code, I assume, you have a set of posts and you are retrieving user name based on user id for each post. Then instead of doing it this way, you should use publish composite package to publish related users as well.
Meteor.publishComposite('getPosts', function (postIds) {
return [{
find: function() {
return Posts.find({ _id: { $in: postIds }});
// you can also do -> return Posts.find();
// or -> return Posts.find({ /* or what ever your selector is to get the posts you need*/ });
},
children: [{
find: function(post) {
return Meteor.users.find({
id: post.userId //or the correct field in your post document to get user id
}, {
fields: {
"profile": 1
}
});
}
}}
}]
});
This way your publication will take care of publishing related users along with posts. You don't need to use methods and call them each time.
I'm looking for a way to determine if Meteor.user() is set in a function that can be called both from the server and client side, without raising an error when it is not.
In my specific case I use Meteor server's startup function to create some dummy data if none is set. Furthermore I use the Collection2-package's autoValue -functions to create some default attributes based on the currently logged in user's profile, if they are available.
So I have this in server-only code:
Meteor.startup(function() {
if (Tags.find().fetch().length === 0) {
Tags.insert({name: "Default tag"});
}
});
And in Tags-collection's schema:
creatorName: {
type: String,
optional: true,
autoValue: function() {
if (Meteor.user() && Meteor.user().profile.name)
return Meteor.user().profile.name;
return undefined;
}
}
Now when starting the server, if no tags exist, an error is thrown: Meteor.userId can only be invoked in method calls. Use this.userId in publish functions.
So in other words calling Meteor.user() on the server startup throws an error instead of returning undefined or null or something. Is there a way to determine whether it will do so prior to calling it?
I cannot solve this simply by wrapping the call with if (Meteor.isServer) within the autoValue function, as the autoValue functions are normally called from server side even when invoked by the user, and in these cases everything in my code works fine.
Note that this is related to How to get Meteor.user() to return on the server side?, but that does not address checking if Meteor.user() is available in cases where calling it might or might not result in an error.
On the server, Meteor.users can only be invoked within the context of a method. So it makes sense that it won't work in Meteor.startup. The warning message is, unfortunately, not very helpful. You have two options:
try/catch
You can modify your autoValue to catch the error if it's called from the wrong context:
autoValue: function() {
try {
var name = Meteor.user().profile.name;
return name;
} catch (_error) {
return undefined;
}
}
I suppose this makes sense if undefined is an acceptable name in your dummy data.
Skip generating automatic values
Because you know this autoValue will always fail (and even if it didn't, it won't add a useful value), you could skip generating automatic values for those inserts. If you need a real name for the creator, you could pick a random value from your existing database (assuming you had already populated some users).
Been stuck with this for two days, this is what finally got mine working:
Solution: Use a server-side session to get the userId to prevent
"Meteor.userId can only be invoked in method calls. Use this.userId in publish functions."
error since using this.userId returns null.
lib/schemas/schema_doc.js
//automatically appended to other schemas to prevent repetition
Schemas.Doc = new SimpleSchema({
createdBy: {
type: String,
autoValue: function () {
var userId = '';
try {
userId = Meteor.userId();
} catch (error) {
if (is.existy(ServerSession.get('documentOwner'))) {
userId = ServerSession.get('documentOwner');
} else {
userId = 'undefined';
}
}
if (this.isInsert) {
return userId;
} else if (this.isUpsert) {
return {$setOnInsert: userId};
} else {
this.unset();
}
},
denyUpdate: true
},
// Force value to be current date (on server) upon insert
// and prevent updates thereafter.
createdAt: {
type: Date,
autoValue: function () {
if (this.isInsert) {
return new Date;
} else if (this.isUpsert) {
return {$setOnInsert: new Date};
} else {
this.unset();
}
},
denyUpdate: true
},
//other fields here...
});
server/methods.js
Meteor.methods({
createPlant: function () {
ServerSession.set('documentOwner', documentOwner);
var insertFieldOptions = {
'name' : name,
'type' : type
};
Plants.insert(insertFieldOptions);
},
//other methods here...
});
Note that I'm using the ff:
https://github.com/matteodem/meteor-server-session/ (for
ServerSession)
http://arasatasaygin.github.io/is.js/ (for is.existy)