Most of the interactions with Substrate network is made through RPC interface.
Basic RPC interface is declared this way:
public protocol Rpc: AnyObject {
func send<Request: Encodable, Response: Decodable>(
_ rpcRequest: RpcRequest<Request>,
completion: @escaping (RpcResponse<Response>?, RpcError?) -> Void
)
func send<Request: Encodable, Response: Decodable>(
_ rpcRequest: RpcRequest<Request>
) async throws -> RpcResponse<Response>
func sendRequest<Request: Encodable, Response: Decodable>(
_ request: Request,
method: String,
completion: @escaping (Response?, RpcError?) -> Void
)
func sendRequest<Request: Encodable, Response: Decodable>(
_ request: Request,
method: String
) async throws -> Response?
func sendRequest<Response: Decodable>(
method: String,
completion: @escaping (Response?, RpcError?) -> Void
)
func sendRequest<Response: Decodable>(
method: String
) async throws -> Response?
}
So, basically all you can do is send and recieve requests.
Requests can be sent in 3 ways:
1. Using RpcRequest generic struct, which looks like that:
public struct RpcRequest<T: Encodable>: Encodable {
public var jsonrpc = "2.0"
public var id: Int32
public var method: String
public var params: T
}
Here is how one can create an RpcRequest:
let request = RpcRequest(
id: 0,
method: "non_existing_method",
params: Nothing()
)
Nothing here is an empty struct representing nothing, used in RPC client for empty requests or responses:
public struct Nothing: Codable {}
2. By creating a custom Encodable request and providing the required method's name:
func sendRequest<Request: Encodable, Response: Decodable>(
_ request: Request,
method: String,
completion: @escaping (Response?, RpcError?) -> Void
)
3. By providing only the required method's name:
func sendRequest<Response: Decodable>(
method: String
) async throws -> Response?
Results can be recieved via closures or async-await interface:
func sendRequest<Request: Encodable, Response: Decodable>(
_ request: Request,
method: String,
completion: @escaping (Response?, RpcError?) -> Void
)
func sendRequest<Request: Encodable, Response: Decodable>(
_ request: Request,
method: String
) async throws -> Response?