doc.go

/*
Package params provides a namespaced module parameter store.

There are two core components, Keeper and Subspace. Subspace is an isolated
namespace for a parameter store, where keys are prefixed by pre-configured
subspace names which modules provide. The Keeper has a permission to access all
existing subspaces.

Subspace can be used by the individual keepers, which need a private parameter store
that the other keepers cannot modify.

Basic Usage:

1. Declare constant module parameter keys and the globally unique Subspace name:

	const (
		ModuleSubspace = "mymodule"
	)

	const (
		KeyParameter1 = "myparameter1"
		KeyParameter2 = "myparameter2"
	)

2. Define parameters as proto message and define the validation functions:

	message MyParams {
		int64 my_param1 = 1;
		bool my_param2 = 2;
	}

	func validateMyParam1(i interface{}) error {
		_, ok := i.(int64)
		if !ok {
			return fmt.Errorf("invalid parameter type: %T", i)
		}

		// validate (if necessary)...

		return nil
	}

	func validateMyParam2(i interface{}) error {
		_, ok := i.(bool)
		if !ok {
			return fmt.Errorf("invalid parameter type: %T", i)
		}

		// validate (if necessary)...

		return nil
	}

3. Implement the params.ParamSet interface:

	func (p *MyParams) ParamSetPairs() params.ParamSetPairs {
		return params.ParamSetPairs{
			params.NewParamSetPair(KeyParameter1, &p.MyParam1, validateMyParam1),
			params.NewParamSetPair(KeyParameter2, &p.MyParam2, validateMyParam2),
		}
	}

	func ParamKeyTable() params.KeyTable {
		return params.NewKeyTable().RegisterParamSet(&MyParams{})
	}

4. Have the module accept a Subspace in the constructor and set the KeyTable (if necessary):

	func NewKeeper(..., paramSpace params.Subspace, ...) Keeper {
		// set KeyTable if it has not already been set
		if !paramSpace.HasKeyTable() {
			paramSpace = paramSpace.WithKeyTable(ParamKeyTable())
		}

		return Keeper {
			// ...
			paramSpace: paramSpace,
		}
	}

Now we have access to the module's parameters that are namespaced using the keys defined:

	func InitGenesis(ctx sdk.Context, k Keeper, gs GenesisState) {
		// ...
		k.SetParams(ctx, gs.Params)
	}

	func (k Keeper) SetParams(ctx sdk.Context, params Params) {
		k.paramSpace.SetParamSet(ctx, &params)
	}

	func (k Keeper) GetParams(ctx sdk.Context) (params Params) {
		k.paramSpace.GetParamSet(ctx, &params)
		return params
	}

	func (k Keeper) MyParam1(ctx sdk.Context) (res int64) {
		k.paramSpace.Get(ctx, KeyParameter1, &res)
		return res
	}

	func (k Keeper) MyParam2(ctx sdk.Context) (res bool) {
		k.paramSpace.Get(ctx, KeyParameter2, &res)
		return res
	}

NOTE: Any call to SetParamSet will panic or any call to Update will error if any
given parameter value is invalid based on the registered value validation function.
*/
package params