In my cloud function, I take the JSON body and particular elements of it.
const type = request.body.type;
But what if type was optional. And the user didn't have to put it. Is there a way of doing the above without it erroring out.
Because in the instant above, if the user left "type" out of their object, then it would cause an error.
If I correctly understand your question you want to check if there is a type property in the request's body.
The following should do the trick:
if (request.body.type) {
//There is a type, act accordingly
} else {
//No type
}
Related
I am trying to grab information from my firebase database after a particular intent is invoked in my conversation flow.
I am trying to make a function which takes a parameter of user ID, which will then get the highscore for that user, and then say that users highscore back to them.
app.intent('get-highscore', (conv) => {
var thisUsersHighestscore = fetchHighscoreByUserId(conv.user.id);
conv.ask('your highest score is ${thisUsersHighestScore}, say continue to keep playing.');
});
function fetchHighscoreByUserId(userId){
var highscoresRef = database.ref("highscores");
var thisUsersHighscore;
highscoresRef.on('value',function(snap){
var allHighscores= snap.val();
thisUsersHighscore = allHighscores.users.userId.highscore;
});
return thisUsersHighscore;
}
An example of the data in the database:
"highscores" : {
"users" : {
"1539261356999999924819020" : {
"highscore" : 2,
"nickname" : "default"
},
"15393362381293223232222738" : {
"highscore" : 78,
"nickname" : "quiz master"
},
"15393365724084067696560" : {
"highscore" : "32",
"nickname" : "cutie pie"
},
"45343453535534534353" : {
"highscore" : 1,
"nickname" : "friendly man"
}
}
}
It seems like it is never setting any value to thisUsersHighScore in my function.
You have a number of issues going on here - both with how you're using Firebase, how you're using Actions on Google, and how you're using Javascript. Some of these issues are just that you could be doing things better and more efficiently, while others are causing actual problems.
Accessing values in a structure in JavaScript
The first problem is that allHighscores.users.userId.highscore means "In an object named 'allHighscores', get the property named 'users', from the result of that, get the property named 'userId'". But there is no property named "userId" - there are just a bunch of properties named after a number.
You probably wanted something more like allHighscores.users[userId].highscore, which means "In an object named 'allHighscores', get the property named 'users', fromt he result of that, get the property named by the value of 'userId'".
But if this has thousands or hundreds of thousands of records, this will take up a lot of memory. And will take a lot of time to fetch from Firebase. Wouldn't it be better if you just fetched that one record directly from Firebase?
Two Firebase Issues
From above, you should probably just be fetching one record from Firebase, rather than the whole table and then searching for the one record you want. In firebase, this means you get a reference to the path of the data you want, and then request the value.
To specify the path you want, you might do something like
var userRef = database.ref("highscores/users").child(userId);
var userScoreRef = userRef.child( "highscore" );
(You can, of course, put these in one statement. I broke them up like this for clarity.)
Once you have the reference, however, you want to read the data that is at that reference. You have two issues here.
You're using the on() method, which fetches the value once, but then also sets up a callback to be called every time the score updates. You probably don't need the latter, so you can use the once() method to get the value once.
You have a callback function setup to get the value (which is good, since this is an async operation, and this is the traditional way to handle async operations in Javascript), but you're returning a value outside of that callback. So you're always returning an empty value.
These suggest that you need to make fetchHighScoreByUserId() an asynchronous function as well, and the way we have to do this now is to return a Promise. This Promise will then resolve to an actual value when the async function completes. Fortunately, the Firebase library can return a Promise, and we can get its value as part of the .then() clause in the response, so we can simplify things a lot. (I strongly suggest you read up on Promises in Javascript and how to use them.) It might look something like this:
return userScoreRef.once("value")
.then( function(scoreSnapshot){
var score = scoreSnapshot.val();
return score;
} );
Async functions and Actions on Google
In the Intent Handler, you have a similar problem as above. The call to fetchHighScoreByUserId() is async, so it doesn't finish running (or returning a value) by the time you call conv.ask() or return from the function. AoG needs to know to wait for an async call to finish. How can it do that? Promises again!
AoG Intent Handlers must return a Promise if there is an asyc call involved.
Since the modified fetchHighScoreByUserId() returns a Promise, we will leverage that. We'll also set our response in the .then() part of the Promise chain. It might look something like this:
app.intent('get-highscore', (conv) => {
return fetchHighscoreByUserId(conv.user.id)
.then( function(highScore){
conv.ask(`Your highest score is ${highScore}. Do you want to play again?`);
} );
});
Two asides here:
You need to use backticks "`" to define the string if you're trying to use ${highScore} like that.
The phrase "Say continue if you want to play again." is a very poor Voice User Interface. Better is directly asking if they want to play again.
Let's say we have the following JSON response:
{
"abcd1234": {
"foo": "bar"
}
}
How would "bar" be accessed in a response parsed body value? In the response, "abcd1234" could be anything. But we want the first key in the object (in JavaScript this would be Object.keys(res)[0]).
Paw makes it easy to parse JSON (and XML) responses and access subfields via their key-path.
This documentation article may help: https://paw.cloud/docs/advanced/reuse-values-from-previous-responses
Insert the Response Parsed Body dynamic value
Set the input request and extract the needed value
In your example, the key path will be:
abcd1234.foo
Though, it seems like you need to access the path without knowing the key before hand. If so, one way would be to use a JavaScript snippet to be able to achieve the behavior you want.
On any field, you may right-click and pick Extensions > JS Script.
Here's a snippet that may fit your needs:
function evaluate(context){
var request = context.getCurrentRequest();
var exchange = request.getLastExchange();
var body = JSON.parse(exchange.responseBody);
var key = Object.keys(body)[0];
var value = body[key].foo;
return value;
};
I'm working on a Firebase Cloud Function. When I log the value of change.after.val() I get a printout of a key-value pair
{ DCBPUTBPT5haNaMvMZRNEpOAWXf3: 'https://m.youtube.com/watch?v=t-7mQhSZRgM' }
rather than simply the value (the URL). Here's my code. What am I not understanding about .val() ? Shouldn't "updated" simply contain the URL?
exports.fanOutLink = functions.database.ref('/userLink').onWrite((change, context) => {
const updated = change.after.val();
console.log(updated);
return null
});
If you want only the URL value, you should include a wildcard in your trigger path for the URL key:
exports.fanOutLink = functions.database.ref('/userLink/{keyId}').onWrite((change, context) => {
console.log('keyId=', context.params.keyId);
const updated = change.after.val();
console.log(updated);
return null
});
In the Realtime Database, data is modeled as a JSON tree. The path specified in an event trigger identifies a node in the tree. The value of the node, being JSON, includes all child nodes. The change parameter for the trigger event refers to the value of the entire node.
I indicated above that you can change the trigger path to refer one level down. An alternative is to access the children of the node using the child() method of DataSnapshot.
Without knowing your use-case, it's hard to be more specific about the trigger event path you should use. Keep in mind that the event fires when any element of the node value changes, whether it be a simple value at the root level, or a value of a child node. It is often the case that you want the trigger to be as specific as possible, to better identify what changed. That's where wildcards in the path are useful. As I showed in the code I posted, the string value of a wildcard is available from the context parameter.
store.select() emits previous store state.
Is it possible to subscribe to changes from "this point forward" without getting the previous store value?
If you are not interested in the first emitted value, you should be able to use the skip operator:
store.select(...).skip(1)...
skip operators need piping now, you can use skip like this:
store.pipe(select(...), skip(1));
In terms of the 'hacky' part, it is a standard practice in ngrx to set an initial state with properties set to null. and that value gets emitted initially. so the first value you get will be null in these cases.
Alternatively you could also consider skipwhile(https://www.learnrxjs.io/learn-rxjs/operators/filtering/skipwhile) and use it like this:
store.pipe(select(...), skipWhile(val => val === undefined));
where undefined is the initial value of the property you are interested in. Rather than setting the initial value of the property to undefined, you could use null as the initial value as well, and change the above skipwhile() accordingly.
Just sharing my thoughts (and solution) after reading #Niz's answer.
This is a perfect, practical example of how to utilize the difference between null and undefined. When you initialize your state with null, you're basically saying:
I don't care about differentiating the nullable future state from the
initial one. I don't care if the user is null because he has signed
out or because he just didn't sign in
However, in some cases this could be insufficient. Think about a case when you need an asynchronous call (implemented in effects) in order to know if you have an active user session. Based on the selection result, you should determine whether to show a login modal or redirect to a content page. With initial user state set to null, you'd pop up that modal and then immediately hide it when that asynchronous call returns a session value.
With initial state set to undefined you can make that differentiation, saying:
Initially, I know nothing about my state, then it's undefined. When I know it should be empty, then I'll set it to null.
Therefor, as a practical solution, I set everything on the app's initialState to undefined. In the example above, I need to know if the login modal should be displayed after the asynchronous call resolves. skipWhile(val => val === undefined) will do the job for sure, but repeating it over and over again feels a little tedious. Plus, it's not really descriptive to our use case. I created a rxjs-custom-operators.ts with a shortened implementation:
import { Observable } from "rxjs";
import { skipWhile } from "rxjs/operators";
export const skipInitial = () => {
return <T>(source: Observable <T>): Observable<T> => {
return source.pipe(skipWhile(value => value === undefined));
};
};
Usage:
navigateOnLoad(): void {
this.store.pipe(select(selectAuthUser), skipInitial()).subscribe((authUser: CognitoUser) => {
// Navigate to login if !authUser, else navigate to content...
});
}
In Meteor, how do I properly return a value from a property (in this case response) from a collection so that I can send it to a data propert? I have tried the following function:
Responses: function(answer) {
return Responses.findOne({answerId: answer.hash.answer});
}
Which I call in the spacebars template as:
data-selected="{{Responses answer=_id}}
When I look at the HTML it says that the data-selected="[object object]" which is not super surprising but I can't figure out how to return just the response value from the match. I can add .response onto the end and it works but gives an expected 'undefined' error I know that it is not reactive. I have seen people use wrapasync but that was for methods, not subscriptions. I should note that there are several responses, so the code would have to be suitable inside a #for loop of answers which the responses variable is keeping track of the input from each user separately.
Thanks!
I'm not sure about data-selected="{{Responses answer=_id}}". Since you're already inside a for loop your html code can simply look like this:
data-selected="{{Responses}}"
Inside your helper function you can then say:
var myResponse = Responses.findOne({answerId: this._id}).response;
if (myResponse != null){
return myResponse;
else {
return "";
}
When the page is still loading and the data is not yet available, myResponse is still null, so the helper returns the empty string "". Shortly thereafter the data becomes available and your data gets returned, without any error in your console.