How do i customize a PersistedModel in loopback ? Let's say i have two models Post and Comment. A Post hasMany Comment but it can have at most 3 comments. How can i implement that without using hooks? Also i need to do it inside a transaction.
I'm coming from java and this is how i would do that:
class Post {
void addComment(Comment c) {
if(this.comments.size() < 3)
this.comments.add(c)
else
throw new DomainException("Comment count exceeded")
}
}
then i would write a service ...
class PostService {
#Transactional
public void addCommentToPost(postId, Comment comment) {
post = this.postRepository.findById(postId);
post.addComment(comment)
this.postRepository.save(post);
}
}
I know i could write something like:
module.exports = function(app) {
app.datasources.myds.transaction(async (models) => {
post = await models.Post.findById(postId)
post.comments.create(commentData); ???? how do i restrict comments array size ?
})
}
i want to be able to use it like this:
// create post
POST /post --> HTTP 201
// add comments
POST /post/id/comments --> HTTP 201
POST /post/id/comments --> HTTP 201
POST /post/id/comments --> HTTP 201
// should fail
POST /post/id/comments --> HTTP 4XX ERROR
What you are asking here is actually one of the good use cases of using operation hooks, beforesave() in particatular. See more about it here here
https://loopback.io/doc/en/lb3/Operation-hooks.html#before-save
However, I'm not so sure about the transaction part.
For that, I'd suggest using a remote method, it gives you complete freedom to use the transaction APIs of loopback.
One thing to consider here is that you'll have to make sure that all comments are created through your method only and not through default loopback methods.
You can then do something like this
// in post-comment.js model file
module.exports = function(Postcomment){
Postcomment.addComments = function(data, callback) {
// assuming data is an object which gives you the postId and commentsArray
const { comments, postId } = data;
Postcomment.count({ where: { postId } }, (err1, count) => {
if (count + commentsArray.length <= 10) {
// initiate transaction api and make a create call to db and callback
} else {
// return an error message in callback
}
}
}
}
You can use validateLengthOf() method available for each model as part of the validatable class.
For more details refer to Loopback Validation
i think i have found a solution.
whenever you want to override methods created by model relations, write a boot script like this:
module.exports = function(app) {
const old = app.models.Post.prototype.__create__comments;
Post.prototype.__create__orders = function() {
// **custom code**
old.apply(this, arguments);
};
};
i think this is the best choice.
Related
I need help with calling a Javascript method from .NET c# backend.
From what I understand, I need to take paymentIntent from my backend and post it to client side, and call stripe.confirmCardPayment
This is how Javascript looks like:
// Pass the failed PaymentIntent to your client from your server
stripe.confirmCardPayment(intent.client_secret, {
payment_method: intent.last_payment_error.payment_method.id
}).then(function(result) {
if (result.error) {
// Show error to your customer
console.log(result.error.message);
} else {
if (result.paymentIntent.status === 'succeeded') {
// The payment is complete!
}
}
});
This is how my .NET c# code looks like:
try
{
var service = new PaymentIntentService();
var options = new PaymentIntentCreateOptions
{
Amount = 1099,
Currency = "usd",
Customer = "{{CUSTOMER_ID}}",
PaymentMethod = "{{PAYMENT_METHOD_ID}}",
Confirm = true,
OffSession = true,
};
service.Create(options);
}
catch (StripeException e)
{
switch (e.StripeError.ErrorType)
{
case "card_error":
// Error code will be authentication_required if authentication is needed
Console.WriteLine("Error code: " + e.StripeError.Code);
var paymentIntentId = e.StripeError.PaymentIntent.Id;
var service = new PaymentIntentService();
var paymentIntent = service.Get(paymentIntentId);
Console.WriteLine(paymentIntent.Id);
break;
default:
break;
}
}
This flow is covered in this guide to accepting a payment. On each of the server-side code examples you can select the ".NET" tab to see the code for your preferred server language.
You haven't shown how you're initially collecting payment details, so I assume you're using a payment method already attached to a known customer. YOu've also not shown how you're sending the payment data back to the client, but in your javascript snippets it looks like you have the entire intent object. I wouldn't recommend that, and suggest instead sending only what you need. Here, say, just a client_secret and payment_method_id to use in confirmCardPayment.
I'm writing an api to try featherjs with its mongoose adapter. I want my GET /books/ endpoint to only return books with the private attribute set to false. Should I use a before hook? If that's the case, how do I prevent users from running custom queries in my endpoint? Should I manually empty the params object?
You need to create a before hook in books.hooks.js
const books_qry = require('../../hooks/books_qry');
module.exports = {
before: {
all: [],
find: [books_qry()],
...
Create /src/hooks/books_qry.js
module.exports = function () {
return function (context) {
//You have 2 choices to change the context.params.query
//overwrite any request for a custom query
context.params.query = { private: false };
//or add a query param to the request for a custom query
context.params.query.private = false
//check the updated context.params.query
console.log(context.params.query);
return context;
}
}
Select one of the choices that you need. Since I never used mongoose at the moment, check the documentation in order to create a valid query (btw above example works for mongodb adapter)
Heroku recently posted a list of some good tips for postgres. I was most intreged by the Track the Source of Your Queries section. I was curious if this was something that's possible to use with Sequelize. I know that sequelize has hooks, but wasn't sure if hooks could be used to make actual query string adjustments.
I'm curious if it's possible to use a hook or another Sequelize method to append a comment to Sequelize query (without using .raw) to keep track of where the query was called from.
(Appending and prepending to queries would also be helpful for implementing row-level security, specifically set role / reset role)
Edit: Would it be possible to use sequelize.fn() for this?
If you want to just insert a "tag" into the SQL query you could use Sequelize.literal() to pass a literal string to the query generator. Adding this to options.attributes.include will add it, however it will also need an alias so you would have to pass some kind of value as well.
Model.findById(id, {
attributes: {
include: [
[Sequelize.literal('/* your comment */ 1'), 'an_alias'],
],
},
});
This would produce SQL along the lines of
SELECT `model`.`id`, /* your comment */ 1 as `an_alias`
FROM `model` as `model`
WHERE `model`.`id` = ???
I played around with automating this a bit and it probably goes beyond the scope of this answer, but you could modify the Sequelize.Model.prototype before you create a connection using new Sequelize() to tweak the handling of the methods. You would need to do this for all the methods you want to "tag".
// alias findById() so we can call it once we fiddle with the input
Sequelize.Model.prototype.findById_untagged = Sequelize.Model.prototype.findById;
// override the findbyId() method so we can intercept the options.
Sequelize.Model.prototype.findById = function findById(id, options) {
// get the caller somehow (I was having trouble accessing the call stack properly)
const caller = ???;
// you need to make sure it's defined and you aren't overriding settings, etc
options.attributes.include.push([Sequelize.literal('/* your comment */ 1'), 'an_alias']);
// pass it off to the aliased method to continue as normal
return this.findById_untagged(id, options);
}
// create the connection
const connection = new Sequelize(...);
Note: it may not be possible to do this automagically as Sequelize has use strict so the arguments.caller and arguments.callee properties are not accessible.
2nd Note: if you don't care about modifying the Sequelize.Model prototypes you can also abstract your calls to the Sequelize methods and tweak the options there.
function Wrapper(model) {
return {
findById(id, options) {
// do your stuff
return model.findById(id, options);
},
};
}
Wrapper(Model).findById(id, options);
3rd Note: You can also submit a pull request to add this functionality to Sequelize under a new option value, like options.comment, which is added at the end of the query.
This overrides the sequelize.query() method that's internally used by Sequelize for all queries to add a comment showing the location of the query in the code. It also adds the stack trace to errors thrown.
const excludeLineTexts = ['node_modules', 'internal/process', ' anonymous ', 'runMicrotasks', 'Promise.'];
// overwrite the query() method that Sequelize uses internally for all queries so the error shows where in the code the query is from
sequelize.query = function () {
let stack;
const getStack = () => {
if (!stack) {
const o = {};
Error.captureStackTrace(o, sequelize.query);
stack = o.stack;
}
return stack;
};
const lines = getStack().split(/\n/g).slice(1);
const line = lines.find((l) => !excludeLineTexts.some((t) => l.includes(t)));
if (line) {
const methodAndPath = line.replace(/(\s+at (async )?|[^a-z0-9.:/\\\-_ ]|:\d+\)?$)/gi, '');
if (methodAndPath) {
const comment = `/* ${methodAndPath} */`;
if (arguments[0]?.query) {
arguments[0].query = `${comment} ${arguments[0].query}`;
} else {
arguments[0] = `${comment} ${arguments[0]}`;
}
}
}
return Sequelize.prototype.query.apply(this, arguments).catch((err) => {
err.fullStack = getStack();
throw err;
});
};
I'm trying to use the Steam Community (steamcommunity) npm package along with meteorhacks:npm Meteor package to retreive a user's inventory. My code is as follows:
lib/methods.js:
Meteor.methods({
getSteamInventory: function(steamId) {
// Check arguments for validity
check(steamId, String);
// Require Steam Community module
var SteamCommunity = Meteor.npmRequire('steamcommunity');
var community = new SteamCommunity();
// Get the inventory (730 = CSGO App ID, 2 = Valve Inventory Context)
var inventory = Async.runSync(function(done) {
community.getUserInventory(steamId, 730, 2, true, function(error, inventory, currency) {
done(error, inventory);
});
});
if (inventory.error) {
throw new Meteor.Error('steam-error', inventory.error);
} else {
return inventory.results;
}
}
});
client/views/inventory.js:
Template.Trade.helpers({
inventory: function() {
if (Meteor.user() && !Meteor.loggingIn()) {
var inventory;
Meteor.call('getSteamInventory', Meteor.user().services.steam.id, function(error, result) {
if (!error) {
inventory = result;
}
});
return inventory;
}
}
});
When trying to access the results of the call, nothing is displayed on the client or through the console.
I can add console.log(inventory) inside the callback of the community.getUserInventory function and receive the results on the server.
Relevant docs:
https://github.com/meteorhacks/npm
https://github.com/DoctorMcKay/node-steamcommunity/wiki/CSteamUser#getinventoryappid-contextid-tradableonly-callback
You have to use a reactive data source inside your inventory helper. Otherwise, Meteor doesn't know when to rerun it. You could create a ReactiveVar in the template:
Template.Trade.onCreated(function() {
this.inventory = new ReactiveVar;
});
In the helper, you establish a reactive dependency by getting its value:
Template.Trade.helpers({
inventory() {
return Template.instance().inventory.get();
}
});
Setting the value happens in the Meteor.call callback. You shouldn't call the method inside the helper, by the way. See David Weldon's blog post on common mistakes for details (section Overworked Helpers).
Meteor.call('getSteamInventory', …, function(error, result) {
if (! error) {
// Set the `template` variable in the closure of this handler function.
template.inventory.set(result);
}
});
I think the issue here is you're calling an async function inside your getSteamInventory Meteor method, and thus it will always try to return the result before you actually have the result from the community.getUserInventory call. Luckily, Meteor has WrapAsync for this case, so your method then simply becomes:
Meteor.methods({
getSteamInventory: function(steamId) {
// Check arguments for validity
check(steamId, String);
var community = new SteamCommunity();
var loadInventorySync = Meteor.wrapAsync(community.getUserInventory, community);
//pass in variables to getUserInventory
return loadInventorySync(steamId,730,2, false);
}
});
Note: I moved the SteamCommunity = Npm.require('SteamCommunity') to a global var, so that I wouldn't have to declare it every method call.
You can then just call this method on the client as you have already done in the way chris has outlined.
At a loss on this one.
I'm using Ember and Ember data. I've got this extra implementation of ic-ajax to make GET, POST and PUT calls. Anyway, i'm trying to make a GET call then turn those results into model instances.
return this.GET('/editor')
.then((data) => {
return data.drafts.map((draftData) => {
let draft = this.store.find('draft',draftData.id);
console.log(draft.get('type'));
return draft;
});
});
My API returns proper data as data.drafts. This map is supposed to return an array of promises that resolve to draft models. It does not. It resolves to a draft model that has id, date, and title. But that's it. I have 25 others attributions.
In another part of the application i'm getting drafts using findAll on the model. And those models look fine. But when I try store.findRecord('draft',id) i get these fake objects.
-- edit
This is what my ReOpenClass method looks like for getting an array of objects from the server and turning them into ember objects
search(critera) {
let query = { search: critera };
let adapter = this.store.adapterFor('application');
let url = adapter.buildURL('article','search');
return adapter.ajax(url,'GET', { data: query }).then(response => {
let articleRecords = response.articles.map((article) => {
let record;
try {
record = this.store.createRecord('article', article);
} catch(e) {
record = this.store.peekRecord('article', article.id);
}
return record;
});
return articleRecords;
});
},
So far I can't find a better way to pull this off.