Develop Reference

How to get field names as an array from json in Kotlin

I am parsing the below sample json using retrofit in android:
{
"success": true,
"timestamp": 1664080564,
"base": "EUR",
"date": "2022-09-25",
"rates": {
"AED": 3.559105,
"AFN": 86.151217,
"ALL": 116.321643,
"AMD": 404.265711
}
}
As you can see there is no array in this json data, but I want the values of rates as a list or a map so that I can get "AED, AFN, ALL, AMD" as an array too. How can i achieve that using retrofit?

You can define rates as a Map<String, Double> in your data class and Retrofit will automatically parse the rates in form of a Map.
data class MyModel(
val success: Boolean,
val timestamp: Long,
val base: String,
val date: String,
val rates: Map<String, Double>
)
so that I can get "AED, AFN, ALL, AMD" as an array too.
For this you can simply use rates.keys to get all the keys.

How do you stop Retrofit looking for embedded objects in one-to-many relationships?

If I have a one-to-many Android Room relationship between two tables, expressed like this (using an example cut and paste from the Android developers site):
#Entity
data class User(
#PrimaryKey val userId: Long,
val name: String,
val age: Int
)
#Entity
data class Playlist(
#PrimaryKey val playlistId: Long,
val userCreatorId: Long,
val playlistName: String
)
data class UserWithPlaylists(
#Embedded val user: User,
#Relation(
parentColumn = "userId",
entityColumn = "userCreatorId"
)
val playlists: List<Playlist>
)
then when I use Retrofit2 to get the nested one-to-many object UserWithPlaylists from an API it's expecting JSON that looks more or less like this:
{
"user" : {
"userID": 1,
"name": "whatever",
"age": 10
},
"playlists": [
{
"playlistId": 0,
"playlistName": "whatever"
},
{
"playlistId": 1,
"playlistName": "whatever"
}
]
}
But my api (and as far as I can tell, most APIs) doesn't embed the user details in "user {}" like that. It just shows the user details unembedded, like this:
{
"userID": 1,
"name": "whatever",
"age": 10,
"playlists": [
{
"playlistId": 0,
"playlistName": "whatever"
},
{
"playlistId": 1,
"playlistName": "whatever"
}
]
}
So Retrofit2 would be able to create the playlists, but it won't find a user{} object so I would end up with empty user objects but populated playlist objects.
How would I force Retrofit2 look for the user details unembedded?
Apologies for my roundabout way of asking this question. I don't know the proper terminology for all of this, which has made it difficult for me to search.
thanks!
John

Error: "data must only contain string values" firebase cloud messaging

I'm trying to send some data from my node.js server to an android client via FCM(Firebase Cloud Messaging). I get the following error: "data must only contain string values" when sending it. My data contains 2 JSONObjects. Do I have to convert them to strings or what is the way to go here? Thanks.
var message = {
notification:{
"title": "Alert!",
"body": position[0] + " has left Area: " + activeGeofences[i][1].name
},
data:{
Geofence: activeGeofences[i][1],
Position: position[1]
},
token: activeGeofences[i][0]
};

To convert any JSON objects to a string, you can use JSON.stringify(). On the receiving side you can then use JSON.parse() (or your platform's equivalent) to parse the string back into a tree structure.

You can also do this, since it seemed more accurate to me
data: {
key1: "value1",
key2: "value2",
}
you just have to make sure that value1 or value2 or any n key's value pair is string if its a int or anything else it would throw the error. This could save you from parsing thing.

Inside data object data type should be always strings.
If you will pass type a number data type an error will occur.
let message = {
notification: {
title: payload.title,
body: payload.message,
},
data: {
name: 'sds',
type: '2',
_id: 'sdsd',
},
token: deviceToken,
};

Designing Data structure for Firebase

Warning: My query would be more theoretical (sorry programmers, please bear with me). I am trying to get some idea on how to define the database structure for use in Firebase.
I am exploring the use of Firebase as a backend for a Review app (in Android) I am trying to build.
The app provides product details and review for products of different kinds. So here is an example use case.
The products displayed in the app are of same type (say smartphones). In this use case, defining the database structure is easier. For every phone, I simply need to save the phone specs to Firebase and retrieve them into my app.
Root
|
+--Smartphone
|
+--Manufacturer Name
+--Screen Size
+--Screen Density
+--Processor
+--RAM,...
The products displayed in the app are of different type (say smartphones, Car, Book,...). In this use case, defining the database structure becomes complex. I can simply define the data structure like
Root
|
+--Product
|
+--Manufacturer Name
+--Screen Size
+--Screen Density
+--Processor
+--RAM
+--Fuel type (Petrol/Diesel/Electric)
+--Vehicle Type (Sedan/Hatchback)
+--Vehicle Price,...
However, the problem with above data structure is, when I am trying to make a product review for a smartphone, the data related to Car will remain blank. Same will be the case for a product review of a Car.
This problem can be solved by using Flattening the data structure. This is where I am confused.
Root
|
+--Smartphone
| |
| +--Manufacturer Name
| +--Screen Size
| +--Screen Density
| +--Processor
| +--RAM
|
+--Car
|
+--Fuel type (Petrol/Diesel/Electric)
+--Vehicle Type (Sedan/Hatchback)
+--Vehicle Price,...
However, all product reviews will be displayed in a single activity/fragment. Hence, there will not be different activities/fragments for every product type. Could someone provide me a clear picture of using flattened data structures in my use case?
Regards

You can structure your database like this:
products: {
smartphones: {
smartphone1: {
name: "Best Phone",
ram: "6 GB",
screen: "5.5 inch"
reviews: {
review1: true,
review2: true
}
}
},
cars: {
car1: {
name: "Lightning"
reviews: {
review3: true,
review4: true,
review5: true
}
}
}
},
product-review: {
review1: {
submittedBy: "Conqueror",
message: "Best phone at this price",
timestamp: 1472405901
},
review2: {
submittedBy: "Magic Blaster",
message: "Pros: RAM, Cons: Everything else.",
timestamp: 1472405901
},
review3: {
submittedBy: "Boss",
message: "Excellent Car",
timestamp: 1472405901
},
...
}
Every product(smartphone1, car1 etc..) contains a reviews node, so you can easily load the linked reviews of a particular product.
You can generate timestamps for the nodes you want. You can add it for smartphone1, car1 etc.. but it is not required. But reviews by user require timestamp because you should display when the user has posted a review.
Have a look at this answer to know how to generate timestamps and to convert timestamp back into displayable date:
DateFormat sdf = new SimpleDateFormat("MM-dd-yyyy hh:mm:ss a");
Date someDate = (new Date(timestamp));
return sdf.format(someDate);
You can store user reviews in their individual nodes.
users: {
abcdefghijklm: { // User UID
name: "Conqueror",
reviews: {
review1: smartphone1,
review7: car1
}
},
nopqrstuvwxyz: {
name: "Magic Blaster",
reviews: {
review2: smartphone1
}
}
}
To get the reviews of a specific user, you can get the user's uid and use it to display reviews. Unfortunately, I have never used Firebase on Android, in Javascript, I would do it like this:
firebase.database().ref('users/'+userUID+'/reviews').on('value', function(snapshot) {
firebase.database().ref('product-review/'+snapshot.key).on('value', function(reviewSnapshot) {
console.log(reviewSnapshot.val().message);
});
});
If you want to only see the review of user "Conqueror", set userUID to his unique id. Here is the official documentation on Firebase for Android to retrieve data from database.

Here is the flattest database structure that I can think of. For the products node, you can also use the third structure in your question, it will only affect the logic on how to map the item in your app.
products: {
item1: {
type: "smartphone",
manufacturer_name: "some value",
screen_size: "some value",
screen_density: "some value",
processor: "some value",
ram: "some value"
},
item2: {
type: "car",
fuel_type: "some value",
vehicle_type: "some value",
vehicle_price: "some value"
}
},
users: {
user1: {
name: "some value",
email: "some value"
},
user2: {
name: "some value",
email: "some value"
},
},
products_reviews: {
item1: {
user1: ewview1,
user2: review2
},
item2: {
user2: review3
}
},
users_reviews: {
user1: {
item1: review1
},
user2: {
item1: review2,
item2: review3
}
},
reviews: {
review1: {
text: "this is my review",
timestamp: 1472488486000
},
review2: {
text: "this is my review",
timestamp: 1472488486000
},
review3: {
text: "this is my review",
timestamp: 1472488486000
}
}
Now you should be able to retrieve all reviews from each user and also retrieve all reviews for each product.
Comment here if you have questions, hope this helps :)

Getting contact.id after saving Cordova contact plugin

I need to get back the contact id after it is saved in order to save it to my online database. However the cordova contact.save() method does not return an id after execution.
Here is my logic:
if ($scope.contact.id === undefined) {
contact.save();
console.log("Contact ID is:", savedContact.id);
table.insert({ id: contact.id.value, firstname: name.givenName, lastname: name.familyName, homephone: phoneNumbers[0].value, mobilephone: phoneNumbers[1].value, email: emails[0].value });
}
This does not work.
Is there any way to retrieve the id for the contact without having to search the phones contact list using a phone number like this:
if ($scope.contact.id === undefined) {
contact.save();
var savedContact = navigator.contacts.find({ "phoneNumbers[0]": phoneNumbers[0].value });
console.log("Contact ID is:", savedContact.id);
table.insert({ id: contact.id.value, firstname: name.givenName, lastname: name.familyName, homephone: phoneNumbers[0].value, mobilephone: phoneNumbers[1].value, email: emails[0].value });
}
The above seems like way too much overhead. Not to mention it may not even return the correct contact as a phone number may not be unique.(If someone saves the contact twice with different information)

contact.save() can take two callbacks, success and failure. The success callback should return your newly saved contact (which would include the id.)
if ($scope.contact.id === undefined) {
contact.save(contactSuccess, contactFailure);
}
function contactSuccess(newContact) {
console.log("Contact ID is:", newContact.id);
table.insert({ id: contact.id.value, firstname: name.givenName, lastname: name.familyName, homephone: phoneNumbers[0].value, mobilephone: phoneNumbers[1].value, email: emails[0].value });
}
function contactError(err) {
//bb10 fires multiple error callbacks with empty errors
if (err) {
console.log(err);
}
}
Since it looks like you are using Angular, check out the ngCordova project. It provides some nice wrappers around some plugins that make everything a bit more readable. Here is the relevant excerpt from their contacts docs:
$cordovaContacts.save($scope.contactForm).then(function(savedContact) {
console.log("Contact ID is:", newContact.id);
table.insert({ id: contact.id.value, firstname: name.givenName, lastname: name.familyName, homephone: phoneNumbers[0].value, mobilephone: phoneNumbers[1].value, email: emails[0].value });
}, function(err) {
if (err) {
console.log(err);
}
});