The AppModule interface includes a number of functions for use in initializing and exporting GenesisState for the chain. The ModuleBasicManager calls these functions on each module when starting, stopping or exporting the chain. Here is a very basic implementation that you can expand upon.
Go to x/nameservice/genesis.go and add the following code:
package nameservice
import (
"fmt"
sdk "github.com/cosmos/cosmos-sdk/types"
abci "github.com/tendermint/tendermint/abci/types"
)
type GenesisState struct {
WhoisRecords []Whois `json:"whois_records"`
}
func NewGenesisState(whoIsRecords []Whois) GenesisState {
return GenesisState{WhoisRecords: nil}
}
func ValidateGenesis(data GenesisState) error {
for _, record := range data.WhoisRecords {
if record.Owner == nil {
return fmt.Errorf("Invalid WhoisRecord: Value: %s. Error: Missing Owner", record.Value)
}
if record.Value == "" {
return fmt.Errorf("Invalid WhoisRecord: Owner: %s. Error: Missing Value", record.Owner)
}
if record.Price == nil {
return fmt.Errorf("Invalid WhoisRecord: Value: %s. Error: Missing Price", record.Value)
}
}
return nil
}
func DefaultGenesisState() GenesisState {
return GenesisState{
WhoisRecords: []Whois{},
}
}
func InitGenesis(ctx sdk.Context, keeper Keeper, data GenesisState) []abci.ValidatorUpdate {
for _, record := range data.WhoisRecords {
keeper.SetWhois(ctx, record.Value, record)
}
return []abci.ValidatorUpdate{}
}
func ExportGenesis(ctx sdk.Context, k Keeper) GenesisState {
var records []Whois
iterator := k.GetNamesIterator(ctx)
for ; iterator.Valid(); iterator.Next() {
name := string(iterator.Key())
var whois Whois
whois = k.GetWhois(ctx, name)
records = append(records, whois)
}
return GenesisState{WhoisRecords: records}
}A few notes about the above code:
ValidateGenesis()validates the provided genesis state to ensure that expected invariants holdDefaultGenesisState()is used mostly for testing. This provides a minimal GenesisState.InitGenesis()is called on chain start, this function imports genesis state into the keeper.ExportGenesis()is called after stopping the chain, this function loads application state into a GenesisState stuct to later be exported togenesis.jsonalongside data from the other modules.