Indy-SDK Developer Walkthrough #4, Rust Edition
[ Python | .NET | Node.js | Objective C | Java]
Setup your workstation with an indy development virtual machine (VM). See prerequisites.
In your normal workstation operating system (not the VM), open a rust editor of your choice and paste the code from template.rs into a new doc. We will be modifying this code in later steps.
Save the doc as write-schema-and-cred-def.rs
This is a simple app framework into which you'll plug the code you'll be writing.
We need to give the SDK some context that it will need to deal with an indy ledger. This requires us to point the SDK at some genesis transactions that tell the SDK how to contact the ledger on the network and how to trust that the nodes it contacts possess appropriate keys. We also need to create a wallet so the SDK can store DIDs and the key material we're going to use. Also, we need to create a trust anchor identity that has privileges to create schemas and credential definitions.
All of these steps are similar to those in simpler how-tos, such as "Write a DID and Query Its Verkey". We'll get this housekeeping out of the way in a single step here, rather than dwelling on its details.
Copy the contents of step2.rs into
write-schema-and-cred-def.rs on top of the Step 2 code goes here placeholder comment.
Save the updated version of write-schema-and-cred-def.rs.
Study the changes. Scaffolding code like this is likely to appear in anything that uses indy.
Now we need to create and define a schema. Schemas in indy are very simple JSON documents that specify their name and version, and that list attributes that will appear in a credential. Today, they do not describe data type, recurrence rules, nesting, and other elaborate constructs. There is work underway to make them fancier; visit #indy-sdk on Rocket.Chat to learn more.
Copy the contents of step3.rs into
write-schema-and-cred-def.rs on top of the Step 3 code goes here placeholder comment.
Save the updated version of write-schema-and-cred-def.rs.
Notice how this schema is submitted to the ledger by the steward identity we created previously.
Next, we create a credential definition. This references the schema that we just added, and announces who is going to be issuing credentials with that schema (our trust anchor identity, in this case), what type of signature method they plan to use ("CL" = "Camenisch Lysyanskya", the default method used for zero-knowledge proofs by indy), how they plan to handle revocation, and so forth.
Copy the contents of step4.rs into
write-schema-and-cred-def.rs on top of the Step 4 code goes here placeholder comment.
Save the updated version of write-schema-and-cred-def.rs.
Run the finished code and observe the whole sequence.
You might try the "Issue a Credential" how-to, which can be done in only one step once you complete this one.