In fact I do not how to write it because I have an array. here is sample code
rets = []
funcA(data[0], function(err, ret) {
rets.push(ret)
funcA(data[1], function(err, ret) {
rets.push(ret)
funcB(rets, function(err) {
})
})
})
because I don't know the size of data, so I cannot hardcode like above.
How can I do that? And even I can do that, it becomes deep nested callbacks which I would like to avoid.
Why don't you use recursion instead of nested callbacks ?
Related
I'm using the Nodejs library for talking to Jira called jira-connector. I can get all of the boards on my jira instance by calling
jira.board.getAllBoards({ type: "scrum"})
.then(boards => { ...not important stuff... }
the return set looks something like the following:
{
maxResults: 50,
startAt: 0,
isLast: false,
values:
[ { id: ... } ]
}
then while isLast === false I keep calling like so:
jira.board.getAllBoards({ type: "scrum", startAt: XXX })
until isLast is true. then I can organize all of my returns from promises and be done with it.
I'm trying to reason out how I can get all of the data on pages with Ramda, I have a feeling it's possible I just can't seem to sort out the how of it.
Any help? Is this possible using Ramda?
Here's my Rx attempt to make this better:
const pagedCalls = new Subject();
pagedCalls.subscribe(value => {
jira.board.getAllBoards({ type:"scrum", startAt: value })
.then(boards => {
console.log('calling: ' + value);
allBoards.push(boards.values);
if (boards.isLast) {
pagedCalls.complete()
} else {
pagedCalls.next(boards.startAt + 50);
}
});
})
pagedCalls.next(0);
Seems pretty terrible. Here's the simplest solution I have so far with a do/while loop:
let returnResult = [];
let result;
let startAt = -50;
do {
result = await jira.board.getAllBoards( { type: "scrum", startAt: startAt += 50 })
returnResult.push(result.values); // there's an array of results under the values prop.
} while (!result.isLast)
Many of the interactions with Jira use this model and I am trying to avoid writing this kind of loop every time I make a call.
I had to do something similar today, calling the Gitlab API repeatedly until I had retrieved the entire folder/file structure of the project. I did it with a recursive call inside a .then, and it seems to work all right. I have not tried to convert the code to handle your case.
Here's what I wrote, if it will help:
const getAll = (project, perPage = 10, page = 1, res = []) =>
fetch(`https://gitlab.com/api/v4/projects/${encodeURIComponent(project)}/repository/tree?recursive=true&per_page=${perPage}&page=${page}`)
.then(resp => resp.json())
.then(xs => xs.length < perPage
? res.concat(xs)
: getAll(project, perPage, page + 1, res.concat(xs))
)
getAll('gitlab-examples/nodejs')
.then(console.log)
.catch(console.warn)
The technique is pretty simple: Our function accepts whatever parameters are necessary to be able to fetch a particular page and an additional one to hold the results, defaulting it to an empty array. We make the asynchronous call to fetch the page, and in the then, we use the result to see if we need to make another call. If we do, we call the function again, passing in the other parameters needed, the incremented page number, and the merge of the current results and the ones just received. If we don't need to make another call, then we just return that merged list.
Here, the repository contains 21 files and folders. Calling for ten at a time, we make three fetches and when the third one is complete, we resolve our returned Promise with that list of 21 items.
This recursive method definitely feels more functional than your versions above. There is no assignment except for the parameter defaulting, and nothing is mutated along the way.
I think it should be relatively easy to adapt this to your needs.
Here is a way to get all the boards using rubico:
import { pipe, fork, switchCase, get } from 'rubico'
const getAllBoards = boards => pipe([
fork({
type: () => 'scrum',
startAt: get('startAt'),
}),
jira.board.getAllBoards,
switchCase([
get('isLast'),
response => boards.concat(response.values),
response => getAllBoards(boards.concat(response.values))({
startAt: response.startAt + response.values.length,
})
]),
])
getAllBoards([])({ startAt: 0 }) // => [...boards]
getAllBoards will recursively get more boards and append to boards until isLast is true, then it will return the aggregated boards.
Clearly, I am doing something wrong with ReactiveVar because I cannot get it to work as I expect it should.
I am trying to set the value of an ReactiveVar by calling a Meteor.call method which returns the list of usernames. But it does not update when the usernames get changed in another part of the app.
I tried both:
Template.qastatistics.created = function () {
this.trackUsernames = new ReactiveVar(false);
var instance = Template.instance();
Meteor.call('trackUsernames', function (err, data) {
instance.trackUsernames.set(data);
});
};
and:
Template.qastatistics.helpers({
users: function () {
var usernames,
instance = Template.instance();
if (instance.trackUsernames.get() === false) {
Meteor.call('trackUsernames', function (err, data) {
instance.trackUsernames.set(data);
});
}
usernames = instance.trackUsernames.get();
...
But neither updates the list of usernames when these change in the database.
Is this even possible with ReactiveVars or have I completely misunderstood them?
EDIT: The usernames I mention are not from Meteor.users collection, but rather a distinct call from another collection that has usernames in it.
Fist of all I would use the onCreated function instead of defining created. That's a little more extendable and it's the new API. created is just kept around for backwards compatibility.
About your problem. You are right, you seem to have misunderstood what ReactiveVars do. They are a reactive data source. That means that when you call myReactiveVar.get in some Tracker.autorun (aka. reactive computation), the computation will rerun whenever myReactiveVar.set is called.
You got the first part right. Spacebars helpers always run inside their own computation. What you got wrong is thinking that a method call is a reactive action. That means, that you could call trackUsernames and set the trackUsernames ReativeVar again and the value in your template would update itself. But a method is only run once. It doesn't do anything fancy with reactivity.
A method call only transfers data once. When you publish a set of documents (like all users) on the other hand, they will be updated dynamically. Whenever a change happens inside that set of published documents, it will be synced to the client. So in general, it's a better idea to use publications and subscriptions to sync data reactively. If you'd want to use a method for the same thing you'd need to do some kind of polling (so your back in the stone-age again).
The easiest way to implement what you are trying to do is to use Meteor.users.find().fetch(). As it says in the docs fetch registers dependencies for all the documents you are fetching if it's being called from within a reactive computation.
First you'll need to properly set up your publications, so that users can see other users usernames. I'll leave that to you. Then you need to reimplement your helper
Template.qastatistics.helpers({
users: function () {
var usernames = _.pluck(Meteor.users.find().fetch(), 'username');
...
Thanks to suggestions from #kyll, I managed to get what I wanted by publishing the data I need:
server:
cope.publish.usernamesID = Random.id();
Meteor.publish("itemsusernames", function () {
self = this;
var initializing = true;
var handle = Items.find().observeChanges({
added: function (id) {
!initializing && self.changed(
"itemsusernames",
cope.publish.usernamesID,
Items.distinct("p4User"));
},
changed: function (id) {
!initializing && self.changed(
"itemsusernames",
cope.publish.usernamesID,
Items.distinct("p4User"));
},
removed: function (id) {
!initializing && self.changed(
"itemsusernames",
cope.publish.usernamesID,
Items.distinct("p4User"));
}
});
initializing = false;
self.added("itemsusernames", cope.publish.usernamesID, Items.distinct("p4User"));
self.ready();
self.onStop(function () {
handle.stop();
});
});
client:
users: function () {
var usernames = [],
oUsernames = ItemsUsernames.find().fetch();
if (!oUsernames[0]) return [];
usernames = $.map(oUsernames[0], function (value, index) {
if (!isNaN(index)) {
return [value];
}
});
...
And ofcourse: ItemsUsernames = new Mongo.Collection("itemsusernames");
I'm trying to perform a simple count with knex (since it seems to not be supported by bookshelf yet). The following code is working:
bookshelf.knex('hosts').count('id').then(function(total) {
res.send({
meta: {
total: total[0]['count(`id`)']
}
});
});
It just seems odd to me that I have to do total[0]['count('id')'] to get the actual result. Am I doing things right here?
Thanks!
All the results from knex.js are arrays. A query could be successful and simply return 0 results.
Also, you can alias the column directly in the column name (or count() call). Like this:
bookshelf.knex('hosts').count('id as CNT').then(function(total) {
res.send({
meta: {
total: total[0].CNT
}
});
});
Still need to get the first element, but you can reference the column as a normal JSON property.
While knex does return results as arrays, it also has a method for returning the first result, which will be an object--not an array. It's pretty simple to get straight to the count without having to rely on [0] or anything to access your count within an array. For your example, a cleaner solution could be:
bookshelf
.knex("hosts")
.count("id")
.first()
.then(function(total) {
res.send({
meta: {
total: total.count
}
});
});
code for node js
let result = await knex.count("id").from('events').first();
if (result) {
console.log(result.count);
}
this seems to work correctly and is a bit simpler
knex('Quotes').count('quoteBody')
.then((res)=>{
//console.log("rows "+JSON.stringify(res))
console.log("rowspl2 "+res[0]['count(`quoteBody`)'])
})
.catch((err)=>{
console.log("err "+err)
})
or try it like this
knex('Quotes').count('quoteBody', {as: 'rows'})
.then((res)=>{
// console.log("rows "+JSON.stringify(res))
console.log("rowsp "+res[0]['rows'])
})
.catch((err)=>{
console.log("err "+err)
})
Meteor Collections have a transform ability that allows behavior to be attached to the objects returned from mongo.
We want to have autopublish turned off so the client does not have access to the database collections, but we still want the transform functionality.
We are sending data to the client with a more explicit Meteor.publish/Meteor.subscribe or the RPC mechanism ( Meteor.call()/Meteor.methods() )
How can we have the Meteor client automatically apply a transform like it will when retrieving data directly with the Meteor.Collection methods?
While you can't directly use transforms, there is a way to transform the result of a database query before publishing it. This is what the "publish the current size of a collection" example describes here.
It took me a while to figure out a really simple application of that, so maybe my code will help you, too:
Meteor.publish("publicationsWithHTML", function (data) {
var self = this;
Publications
.find()
.forEach(function(entry) {
addSomeHTML(entry); // this function changes the content of entry
self.added("publications", entry._id, entry);
});
self.ready();
});
On the client you subscribe to this:
Meteor.subscribe("publicationsWithHTML");
But your model still need to create a collection (on both sides) that is called 'publications':
Publications = new Meteor.Collection('publications');
Mind you, this is not a very good example, as it doesn't maintain the reactivity. But I found the count example a bit confusing at first, so maybe you'll find it helpful.
(Meteor 0.7.0.1) - meteor does allow behavior to be attached to the objects returned via the pub/sub.
This is from a pull request I submitted to the meteor project.
Todos = new Meteor.Collection('todos', {
// transform allows behavior to be attached to the objects returned via the pub/sub communication.
transform : function(todo) {
todo.update = function(change) {
Meteor.call('Todos_update', this._id, change);
},
todo.remove = function() {
Meteor.call('Todos_remove', this._id);
}
return todo;
}
});
todosHandle = Meteor.subscribe('todos');
Any objects returned via the 'todos' topic will have the update() and the remove() function - which is exactly what I want: I now attach behavior to the returned data.
Try:
let transformTodo = (fields) => {
fields._pubType = 'todos';
return fields;
};
Meteor.publish('todos', function() {
let subHandle = Todos
.find()
.observeChanges({
added: (id, fields) => {
fields = transformTodo(fields);
this.added('todos', id, fields);
},
changed: (id, fields) => {
fields = transformTodo(fields);
this.changed('todos', id, fields);
},
removed: (id) => {
this.removed('todos', id);
}
});
this.ready();
this.onStop(() => {
subHandle.stop();
});
});
Currently, you can't apply transforms on the server to published collections. See this question for more details. That leaves you with either transforming the data on the client, or using a meteor method. In a method, you can have the server do whatever you want to the data.
In one of my projects, we perform our most expensive query (it joins several collections, denormalizes the documents, and trims unnecessary fields) via a method call. It isn't reactive, but it greatly simplifies our code because all of the transformation happens on the server.
To extend #Christian Fritz answer, with Reactive Solution using peerlibrary:reactive-publish
Meteor.publish("todos", function() {
const self = this;
return this.autorun(function(computation) {
// Loop over each document in collection
todo.find().forEach(function(entry) {
// Add function to transform / modify each document here
self.added("todos", entry._id, entry);
});
});
});
I have what should be very simple. I create a new collection, and I want to pass it to a render and add the collection models to the page.
get_results: function(){
$.getJson(this.url,function(response){
this.search_results = new Kitchon.Collections.searchList(response);
console.log(this.search_results);
this.search_results.each(this.render_match);
}
},
render_match: function(model){
console.log(model)
},
This returns an error
Uncaught TypeError: undefined is not a function
my collection has an ordinary structure
_byCid: Object
_byId: Object
_onModelEvent: function () { [native code] }
_removeReference: function () { [native code] }
length: 7
models: Array[7]
__proto__: o
I've tried LOTS of things, but one thing that stuck out was maybe I had to pass
this.search_results.models.each(this.render_match); as that is the actual array, but if I do that I get a Uncaught typeError: Object [object Object],[object Object],...
you lose the execution context when callback function for each method is called
use _.bind(this.render_match, this) when passing callback to make sure that render_match has the right context
and you were getting error because you didn't wrap the callback function for getJson method neither. You have to use underscore bind method there as well.
You should read a bit about javascript this and how to tame it - try here http://yehudakatz.com/2011/08/11/understanding-javascript-function-invocation-and-this/
Correct code should look more or less like this...
get_results: function(){
$.getJSON(this.url, _.bind(function(response){
this.search_results = new Kitchon.Collections.searchList(response);
console.log(this.search_results);
this.search_results.each(_.bind(this.render_match, this));
}, this));
},
render_match: function(model){
console.log(model)
},
Though from what I seee - I assume the code you've shown here is either a model or collection - is handling rendering the view - you shouldn't do that! Models and Collections are only to store and parse data - all rendering and controlling application flow should be done in the View(Controllers) with help of the Router.
$.getJson changes the this reference. Many methods in jquery do that, so the value of this.render_match is null. You pass null to each and it fails.
To solve that, create a reference to this (like var _this = this;) before $.getJson and use it instead of this. Code should be like below:
get_results: function(){
var _this = this;
$.getJson(this.url,function(response){
_this.search_results = new Kitchon.Collections.searchList(response);
console.log(_this.search_results);
_this.search_results.each(_this.render_match);
}
},
render_match: function(model){
console.log(model)
},
Just taking a stab here (I don't know anything about Backbone.js), but isn't this what you are looking for:
$.each(this.search_results, function(index, value) {
alert(index + ': ' + value);
});
Good Luck!