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Version: v5.4.x



Learn how to implement the IBC Module keeper.


In the previous sections, on channel handshake callbacks and port binding in InitGenesis, a reference was made to keeper methods that need to be implemented when creating a custom IBC module. Below is an overview of how to define an IBC module's keeper.

Note that some code has been left out for clarity, to get a full code overview, please refer to the transfer module's keeper in the ibc-go repo.

// Keeper defines the IBC app module keeper
type Keeper struct {
storeKey sdk.StoreKey
cdc codec.BinaryCodec
paramSpace paramtypes.Subspace

channelKeeper types.ChannelKeeper
portKeeper types.PortKeeper
scopedKeeper capabilitykeeper.ScopedKeeper

// ... additional according to custom logic

// NewKeeper creates a new IBC app module Keeper instance
func NewKeeper(
// args
) Keeper {
// ...

return Keeper{
cdc: cdc,
storeKey: key,
paramSpace: paramSpace,

channelKeeper: channelKeeper,
portKeeper: portKeeper,
scopedKeeper: scopedKeeper,

// ... additional according to custom logic

// IsBound checks if the IBC app module is already bound to the desired port
func (k Keeper) IsBound(ctx sdk.Context, portID string) bool {
_, ok := k.scopedKeeper.GetCapability(ctx, host.PortPath(portID))
return ok

// BindPort defines a wrapper function for the port Keeper's function in
// order to expose it to module's InitGenesis function
func (k Keeper) BindPort(ctx sdk.Context, portID string) error {
cap := k.portKeeper.BindPort(ctx, portID)
return k.ClaimCapability(ctx, cap, host.PortPath(portID))

// GetPort returns the portID for the IBC app module. Used in ExportGenesis
func (k Keeper) GetPort(ctx sdk.Context) string {
store := ctx.KVStore(k.storeKey)
return string(store.Get(types.PortKey))

// SetPort sets the portID for the IBC app module. Used in InitGenesis
func (k Keeper) SetPort(ctx sdk.Context, portID string) {
store := ctx.KVStore(k.storeKey)
store.Set(types.PortKey, []byte(portID))

// AuthenticateCapability wraps the scopedKeeper's AuthenticateCapability function
func (k Keeper) AuthenticateCapability(ctx sdk.Context, cap *capabilitytypes.Capability, name string) bool {
return k.scopedKeeper.AuthenticateCapability(ctx, cap, name)

// ClaimCapability allows the IBC app module to claim a capability that core IBC
// passes to it
func (k Keeper) ClaimCapability(ctx sdk.Context, cap *capabilitytypes.Capability, name string) error {
return k.scopedKeeper.ClaimCapability(ctx, cap, name)

// ... additional according to custom logic