I am new to Angular and I am trying to build a simple todo application using it. I have designed a module called TodoServices in which I am creating a User service using the factory method. The code looks something like:
angular.module('TodoServices', ["ngResource"])
.factory('User', function($resource){
return $resource('http://todoapi.rohanchhabra.in/users/:id');
});
The code in my app.js looks like:
var angularApp = angular.module('angularApp', ['TodoServices']);
angularApp.controller('UsersController', function(User){
this.users = {};
this.users = User.query();
});
When I run my application, I get this error: Error link
I think this is because my web service is returning an object which not only has the data but also has a few other things such as a status and messages. Now Is it a wrong way of doing it? Should I just return the array from the back end? What is the actual problem here and how to solve this?
As your error link says:
By default, all resource actions expect objects, except query which expects arrays.
You should use an other function like User.Get() when you're not expecting an array but just a single object.
Related
I was using OMDBapi to get the details of different movies. I successfully fetched the result and it returns a json object like this;
{"Title":"WWA: The Inception","Year":"2001","Rated":"N/A","Released":"26 Oct 2001","Runtime":"N/A","Genre":"Action, Sport","Director":"N/A","Writer":"Jeremy Borash","Actors":"Bret Hart, Jeff Jarrett, Brian James, David Heath","Plot":"N/A","Language":"English","Country":"Australia","Awards":"N/A","Poster":"https://m.media-amazon.com/images/M/MV5BNTEyNGJjMTMtZjZhZC00ODFkLWIyYzktN2JjMTcwMmY5MDJlXkEyXkFqcGdeQXVyNDkwMzY5NjQ#._V1_SX300.jpg","Ratings":[{"Source":"Internet Movie Database","Value":"6.0/10"}],"Metascore":"N/A","imdbRating":"6.0","imdbVotes":"22","imdbID":"tt0311992","Type":"movie","DVD":"N/A","BoxOffice":"N/A","Production":"N/A","Website":"N/A","Response":"True"}
Note that we get this type of object from the api if we want to get a particular movie details and that is what i was doing. Now to show the different details to a user, i started parsing this JSON object which works fine but when i try to get the value of the Value key present inside the Ratings key, it returns undefined.
I am working with react-native. After getting the data, i stored it inside the state, named it as details. Then to get it;
this.state.details.Title //if i wanted to get the Title and it works fine.
Then for Value inside Ratings;
this.state.details.Ratings[0].Value
But it returns undefined.
Also note that this works fine in pure Javascript as i parsed the dict in the browser console in the same way and it returned the correct value.
Here is more code;
componentDidMount() {
this.fetchData();
}
fetchData = async () => {
const response = await fetch(`http://www.omdbapi.com/?i=${this.props.navigation.getParam('i')}&apikey=******`) // where this.props.navigation.getParam('i') is the omdbid of the movie
const result = await response.json()
this.setState({details: result})
}
Here is error log;
undefined is not an object (evaluating 'this.state.details.Ratings[0]')
You're most likely trying to access state object before fetch has done it's job .... it's an async op ... so you should make sure your data is ready before rendering...
if (this.state.details) {
// start rendering...
}
More Explanation
your setState function should be executed right after fetch has finished its job, and since it's an async operation, it's going to take some time ...During that time, render function is executed with no state.details --> causing your issue ...
That's why you should check for state before rendering ... besides, the optional chaining trick Silversky Technology mentioned in his answer
If the value property you are accessing from the object might be not available for all the movies in the data you are getting from API response so it might cause you to error when accessing key from undefined objects.
To overcome the issue there is a way, you can try a fix as below:
this.state.details.Ratings[0]?.Value
The ? symbol lets the javascript not give an error when the value key not available in the object. it will make the accessing of property optional.
When storing objects in states it often causes problems as you are doing in line
this.setState({details: result})
Save result after strigifying it like
JSON.stringify(result)
this.setState({details: result})
Then when fetching form state, parse it back to object by
var result = JSON.parse(this.state.details)
Then you should be able to access it
You can access Ratings[0].Value by
this.state.details.Ratings && this.state.details.Ratings[0].Value
like,
<Text> {this.state.details.Ratings && this.state.details.Ratings[0].Value} </Text>
I am trying to fetch a simple JSON element from express.js. I am trying have React assign it to a state variable on the front end. I am using this code to do so:
componentDidMount() {
fetch("/user")
.then(response => response.json())
.then(result => this.setState({myUser:result}))
}
But when I run typeof myUser after this setState command, it says string instead of object. I've tried using JSON.parse(), etc. But either I get an error or it continues to assign the data as a string rather than JSON. What sort of syntax do I need to use in this fetch-then context to coerce the data assignment to be JSON?
I have read this link:
With this code:
componentDidMount(){
fetch('https://abx.com/data/tool.json').then(response =>{
if (!response.ok) throw Error('Response not ok')
return response.json(); // This is built in JSON.parse wrapped as a Promise
}).then(json => {
this.setState({"sections" : json});
}).catch(err =>{
console.log(err);
});
}
But it doesn't solve the problem. I ran this code directly in my application verbatim. When I run typeof on the variable, it says string instead of object. I looked at other posts on Stack Overflow, but I did not see a solution to this.
I figured out what was going wrong (after many hours of experimenting):
On the server side, I was creating a "homegrown" JSON object using string and variable concatenation. I also tried creating the JSON object by doing this:
var str = "name:" + name + ", department:" + department
var user = {str};
Both of these were not working in subtle ways... despite trying different types of gadgetry on the client side, I couldn't get React to interpret the data as a JSON object. But then I had an idea to construct the JSON on the server side (in Express.js) like this:
var user = {};
user["name"] = name;
user["department"] = department;
That immediately cleared things up on the server side and the client side. When using setState() in React, it now sets the value as an object (which was the goal all along).
I think this can be useful to others... if React doesn't seem to understand the JSON, perhaps it is being sent from the server in a subtly incorrect format.
This is a slightly messy questions. Although it appears I'm asking question about amCharts, I really just trying to figure how to extract an array from HTTP request and then turn it into a variable and place it in to 3-party javacript.
It all starts here, with this question, which was kindly answered by AmCharts support.
As one can see from the plnker. The chart is working. Data for the chart is hard coded:
`var chartData = [{date: new Date(2015,2,31,0,0,0, 0),value:372.10,volume:2506100},{date: new Date(2015,3,1,0, 0, 0, 0),value:370.26,volume:2458100},{date: new Date(2015,3,2,0, 0, 0, 0),value:372.25,volume:1875300},{date: new Date(2015,3,6,0, 0, 0, 0),value:377.04,volume:3050700}];`
So we know the amCharts part works. Know where the problem is changing hard coded data to a json request so it can be dynamic. I don't think this should be tremendously difficult, but for the life of me I can't seem figure it out.
The first issue is I can't find any documentation on .map, .subscribe, or .observable.
So here is a plunker that looks very similar to the first one, however it has an http providers and injectable. It's broken, because I can't figure out how to pull the data from the service an place it into the AmCharts function. I know how pull data from a http provider and display it in template using NgFor, but I don't need it in the template (view). As you can see, I'm successful in transferring the data from the service, with the getTitle() function.
this.chart_data =_dataService.getEntries();
console.log('Does this work? '+this.chart_data);
this.title = _dataService.getTitle();
console.log('This works '+this.title);
// Transfer the http request to chartData to it can go into Amcharts
// I think this should be string?
var chartData = this.chart_data;
So the ultimate question is why can't I use a service to get data, turn that data into a variable and place it into a chart. I suspect a few clues might be in options.json as the json might not be formatted correctly? Am I declaring the correct variables? Finally, it might have something to do with observable / map?
You have a few things here. First this is a class, keep it that way. By that I mean to move the functions you have inside your constructor out of it and make them methods of your class.
Second, you have this piece of code
this.chart_data =_dataService.getEntries().subscribe((data) => {
this.chart_data = data;
});
What happens inside subscribe runs asynchronously therefore this.chart_data won't exist out of it. What you're doing here is assigning the object itself, in this case what subscribe returns, not the http response. So you can simply put your library initialization inside of the subscribe and that'll work.
_dataService.getEntries().subscribe((data) => {
if (AmCharts.isReady) {
this.createStockChart(data);
} else {
AmCharts.ready(() => this.createStockChart(data));
}
});
Now, finally you have an interesting thing. In your JSON you have your date properties contain a string with new Date inside, that's nothing but a string and your library requires (for what I tested) a Date object, so you need to parse it. The problem here is that you can't parse nor stringify by default a Date object. We need to convert that string to a Date object.
Look at this snippet code, I used eval (PLEASE DON'T DO IT YOURSELF, IS JUST FOR SHOWING PURPOSES!)
let chartData = [];
for(let i = 0; i < data[0].chart_data.length; i++) {
chartData.push({
// FOR SHOWING PURPOSES ONLY, DON'T TRY IT AT HOME
// This will parse the string to an actual Date object
date : eval(data[0].chart_data[i].date);
value : data[0].chart_data[i].value;
volume : data[0].chart_data[i].volume;
});
}
Here what I'm doing is reconstructing the array so the values are as required.
For the latter case you'll have to construct your json using (new Date('YOUR DATE')).toJSON() and you can parse it to a Date object using new Date(yourJSON) (referece Date.prototype.toJSON() - MDN). This is something you should resolve in your server side. Assuming you already solved that, your code should look as follows
// The date property in your json file should be stringified using new Date(...).toJSON()
date : new Date(data[0].chart_data[i].date);
Here's a plnkr with the evil eval. Remember, you have to send the date as a JSON from the server to your client and in your client you have to parse it to a Date.
I hope this helps you a little bit.
If the getEntries method of DataService returns an observable, you need to subscribe on it to get data:
_dataService.getEntries().subscribe(
(data) => {
this.chart_data = data;
});
Don't forget that data are received asynchronously from an HTTP call. The http.get method returns an observable (something "similar" to promise) will receive the data in the future. But when the getEntries method returns the data aren't there yet...
The getTitle is a synchronous method so you can call it the way you did.
I'm using node, express, and mongoose.
I have a function that performs a search in a database and sends the response in a JSON format with:
res.jsonp(search_result);
This displays the correctly returned result in the browser as a JSON object. My question is, how do I get that JSON object?
I've tried returning search_result but that gives me null (possibly because asynchronous). I'd also like to not edit the current function (it was written by someone else). I'm calling the function and getting a screen full of JSON, which is what res.jsonp is supposed to do.
Thanks in advance.
Just make a new function that takes this JSON as parameter and place it inside the old one. Example:
// Old function
app.get('/', function(req,res){
// recieve json
json_object = .....
// Get json to your function
processJson(json_object);
// Old function stuff
.
.
.
});
function processJson(json_object) {
// Here you'll have the existing object and can process it
json_object...
}
I am new to angular and trying to consume a basic back end service that I created using laravel. It is a basic Todo application and I am trying to fetch all the users resource for now.
If you go to the following URI, it will give back the all the users in the application:
Link to the URI
The code in my angular file looks like
var testing = angular.module('testing', []);
testing.controller('MainCtrl', function($scope, $http){
$scope.hello = "Hello World!";
$http.get('users.json').success(function(data){
$scope.users = data;
});
});
Now when I pass the URI in the parameter of $http.get method, I don't see any data. I have tried {{ users | json }} in my main index file to see the dump output. It simply doesn't work. But when I copy just the data array in the response and save it to a json file, it works perfectly.
Now the json that is returned from the web service has slightly more information like status and messages. How do I remove them when fetching them in Angular so that it works or is there a way I can have them returned and then extract them somehow from the whole data that has been returned?
If here http://todoapi.rohanchhabra.in/users is response from your server you should update your $http call to :
$http.get('users.json').success(function(response){
$scope.users = response.data;
});
if you requesting json file from your local iis make sure that it can serve .json files