IOS contact list with the same application

Question

I'm looking for a way to create a contact list in iOS for people who have the same application installed. Perhaps this is a way to sync Facebook contacts and send email invitations to these contacts to install the application. The fact is that I need a way to find out what contacts are installed on my phone, and I can not find information about the various approaches to this.

Are there any APIs to help me? Are there several approaches to this? Where do I even start to do this? Creating a list of my contacts is quite simple. Finding out who has my app installed is another story.

Answer 1

The only idea I have is to use a server. You transfer your contacts (the best anonymous ones) to the server, and there you can determine in which contact the application is also installed. The server returns the result.

Basically, all the contact list apps that I know use this approach (like whatsapp).

For hash functions of anonymity check.