Develop Reference

Query problem using sembast (NoSql) with flutter

I'm very new to NoSql databases, and I just want to ask you an easy question about the use of sembast! I'm developing a very simple app with flutter, and I want to get the object inside the array "list" with the "name" equal to 1.
{
"id": 12345,
"list": [{
"name": 1,
"element": [{
"nameItem": "a"
}, {
"nameItem": "b"
}]
}, {
"name": 2,
"element": []
}, {
"name": 3,
"element": []
}]
}
So I want to make a query that retrieves me this information:
{
"name": 1,
"element": [{
"nameItem": "a"
}, {
"nameItem": "b"
}]
}
I've written this code, but it doesn't work: I don't understand how to make a query with a subtag as a key in the json tree.
Future<List<ElementList>> getElementFromList(int name) async{
final finder = Finder(filter: Filter.equals("name", name));
final recordSnapshot = await _elementList.find(await _db, finder: finder);
return recordSnapshot.map((snapshot){
final elementObj = ElementList.fromJson(snapshot.value);
return elementObj;
}).toList();
}
this returns me []. How can I solve the problem?
Thank you in advance!

Sembast queries allow to filter records, not part of a record. If the object you mention is a whole record, you can:
use custom filter to perform the lookup yourself for each record in the database (checking each item in the list field`)
when a record is retrieved, extract the item (doing a similar Map/List manipulation)
See an issue with a complex filtering

Android - Firebase Database Structure

I am developing an android application where older kids can pick up younger kids and walk to school. With the application the authenticated (email and password) younger kid can choose between three adresses to get picked up. As of right now my realtime database looks like this:
Should I make a new node named "Adresses" and have a structure like this below?
Adresses
Sherman Street
username: Jannie
Because I want to retrieve the name of the street and all the users that have chosen the adress in a listview

Your suggested method is good practice: you should try to flatten your data structure as much as possible.
I'd suggest using the user's ID for the membership of each address so it's easy to identify though. This way you can obtain a list of the members of "Sherman Street" from /addresses/Sherman Street and then match the keys listed within there to the users at /users/ with ease.
{
"users": {
"oXrJPVZsnMP3VKp9palSBfdnntk1": { ... },
"xQDx3ntavhV3c02KFRPS8lxYfC62": { ... }
},
"addresses": {
"Sherman Street": {
"members": {
"xQDx3ntavhV3c02KFRPS8lxYfC62": true
}
},
"Wallaby Way": {
"members": {
"oXrJPVZsnMP3VKp9palSBfdnntk1": true
}
}
}
}
You can also add backwards linking too by adding an address field to the user which matches the address name:
{
"users": {
"oXrJPVZsnMP3VKp9palSBfdnntk1": { ... },
"xQDx3ntavhV3c02KFRPS8lxYfC62": {
"username": "Jannie",
"address": "Sherman Street"
}
},
"addresses": {
"Sherman Street": { ... }
}
}
Using both together makes it easy to identify what users have selected which addresses, irrespective of which object you are currently handling within the app.
See the Firebase documentation on database structure for further details on structuring your data like this.

Dynamic object creation with Retrofit

I am not that skilled with Retrofit library and I ran into a problem that i don't know how to handle without restructuring the whole project.
Basically, i have two responses that are very similar, but my code only handles one response.
Here are the responses and what i did, so tell me if there is any way to do this...
{
"cv":[
{
"id":46,
"name":"Ciriculum Vitae",
"description":"Lorem ipsum description is the best description one can write down",
"file":"1482915089-test-test-cv1.pdf",
"file_url":"http://xxxyy/file/46/1482915089-test-test-cv1.pdf",
"type":"cv"
},
...
],
"diploma":[
{
"id":52,
"name":"dasdasdasdsa",
"description":"Random description",
"institution_name":"hello",
"completed_date":"12.12.2016.",
"file":"1482918005-test-test-dasdasdasdsa.pdf",
"file_url":"http://xxxyy/file/52/1482918005-test-test-dasdasdasdsa.pdf",
"type":"diploma"
}
],
...
"certification":[
{
"id":50,
"name":"Certificate of Greatness",
"description":"I have been great at many things so everybody diecided to give me a certificate for it.",
"institution_name":"Certification 3",
"validation_date":"10.06.2017.",
"file":"1482917772-test-test-dasdasdasdsa.pdf",
"file_url":"http://xxxyy/file/50/1482917772-test-test-dasdasdasdsa.pdf",
"type":"certification"
}
],
...
}
Okay this is just a sample, but you can clearly see that these are some documents that have their types. There are 17 types of documents each with different fields.
Logically, I've created 17 different models cv model, diploma model, etc...
The problem arises later in the project when i want to fetch documents that are related to a single candidate, the response then is like so:
Response2
"documents": [
{
"id": 46,
"name": "Ciriculum Vitae",
"type": "cv",
"description": "Lorem ipsum description is the best description one can write down",
"file": "1482915089-test-test-cv1.pdf",
"file_url": "http://xxxyy/file/46/1482915089-test-test-cv1.pdf"
},
{
"id":52,
"name":"dasdasdasdsa",
"description":"Random description",
"institution_name":"hello",
"completed_date":"12.12.2016.",
"file":"1482918005-test-test-dasdasdasdsa.pdf",
"file_url":"http://xxxyy/file/52/1482918005-test-test-dasdasdasdsa.pdf",
"type":"diploma"
},
{
"id": 50,
"name": "Certificate of Greatness",
"type": "certification",
"description": "I have been great at many things so everybody diecided to give me a certificate for it.",
"file": "1482917772-test-test-dasdasdasdsa.pdf",
"file_url": "http://xxxyy/file/50/1482917772-test-test-dasdasdasdsa.pdf"
}
]
}
Now obviously the field 'type' is the type of object that needs to be created. But so far i don't know how to make my models fit into this 2nd response.
What should i do here, guys?
In case you're wondering what my code looks like, here it is...
#SerializedName("cv")
#Expose
private List<Cv> cv = null;
...
#SerializedName("diploma")
#Expose
private List<Diploma> diploma = null;
...
#SerializedName("certification")
#Expose
private List<Certification> certification = null;
EDIT
Actually what i wanted to do is create object dependent on the 'type' parameter and fill it with info i get from the response.
How will i go about doing this?

Want to fetch the data's from JSON file and place it in the respective place?

I can able to fetch the name of the restaurant using id from the json file and show it in this page.
My Doubt is :If we click the “Annalakshmi restaurant”(i.e ,id=1) then it must fetch all the data’s from json with the id=1 and fill the other details of that id to the next page which contains phone number,address....I have to fill the details about that restaurants,we have to fetch from JSON. And at the top i have to keep the images of that restaurant.
My json is:
{
"Categories": {
"restaurant":
{
"res_id": "1",
"res_name": "Annalakshmi Restaurant",
"res_phone":"92600 18001",
"res_time": "12-3PM,7-9PM - Monday(Closed)"
},
{
"res_id": "2",
"res_name": "Kaidi Kitchen",
"res_phone":"090213 37222",
"res_time":"12-3PM,7-10.30PM (All Day)"
},
{
"res_id":"3",``
"res_name":"TajCoromandel",
"res_phone":"044 6600 2827",
"res_time":"24 Hours(All day)"
}
]

How to write and read contents containing complex json data?

friends:
I get a response from remote server as follows on Android:
{
"items": {
"persons": [
{
"id": "200120",
"name": "Bill"
},
{
"id": "200121",
"name": "Jim"
}
],
"tasks": [
{
"id": "001",
"name": "Fetch ten books",
"deadline": "5:30 p.m.",
"scores": "10"
},
{
"id": "002",
"name": "Fetch thirty books",
"deadline": "5:30 p.m.",
"scores": "30"
}
],
"intro": "This is a funny game."
},
"otherObj": []
}
And I want to save it to phones. I do not think it a good choice to save it into databases. However it read not fast if put the response to SharedPreferences file. Is there any other way?

No need to save this data into database as these value are dynamic and will change time to time.
In your Activity, call the API and get JSON as response and then parse this JSON and show it on device.
To store it on device u can use Singleton class also.
For JSON parser refer to http://www.tutorialspoint.com/android/android_json_parser.htm

You can first save your data into objects and at last into Object Array and then Save to database.(If your data is dynamic it is better you only deal with Object not database)
For saving to database you can use
db.beginTransaction();
for(object : ObjectArray){
db.dboperation();
}
db.setTransactionSuccessful();
db.endTransaction();