Hi all,
for my app I want something like the account check in whatsapp.
I mean, when you open your address book in whatsapp you see which user had an existing whatsapp-account.
I know how to get access to the local address book and from my provider (backhand.com) i could receive the registered email-adresses for my app.
But i don’t know how to check this?
I think the only way is to transfer the contacts (hashed) to the server, right?
do not know how backhand work, but you need something like an api-call, which checks your list of contact numbers/mails against your database.
Means --> you are sending the list of phone numbers/emails to your backend, this check ins the database if they are already in there --> the response contains a liste of true or false for each entry
Thanks for explanation. It thought this would be the only possible but i wasn’t sure if this is compatible with data protection act.
Yes, I’m currently not really familiar with the backend 
but I’m working on it! but actually i just had to read some very good literature about the frontend 
Is there a good keyword for google search? maybe i could found some good tutorial.