80 lines
2.8 KiB
Markdown
80 lines
2.8 KiB
Markdown
---
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sidebar_position: 1
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---
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# `x/params`
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> Note: The Params module has been depreacted in favour of each module housing its own parameters.
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## Abstract
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Package params provides a globally available parameter store.
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There are two main types, Keeper and Subspace. Subspace is an isolated namespace for a
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paramstore, where keys are prefixed by preconfigured spacename. Keeper has a
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permission to access all existing spaces.
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Subspace can be used by the individual keepers, which need a private parameter store
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that the other keepers cannot modify. The params Keeper can be used to add a route to `x/gov` router in order to modify any parameter in case a proposal passes.
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The following contents explains how to use params module for master and user modules.
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## Contents
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* [Keeper](#keeper)
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* [Subspace](#subspace)
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* [Key](#key)
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* [KeyTable](#keytable)
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* [ParamSet](#paramset)
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# Keeper
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In the app initialization stage, [subspaces](#subspace) can be allocated for other modules' keeper using `Keeper.Subspace` and are stored in `Keeper.spaces`. Then, those modules can have a reference to their specific parameter store through `Keeper.GetSubspace`.
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Example:
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```go
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type ExampleKeeper struct {
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paramSpace paramtypes.Subspace
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}
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func (k ExampleKeeper) SetParams(ctx sdk.Context, params types.Params) {
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k.paramSpace.SetParamSet(ctx, ¶ms)
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}
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```
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# Subspace
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`Subspace` is a prefixed subspace of the parameter store. Each module which uses the
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parameter store will take a `Subspace` to isolate permission to access.
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## Key
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Parameter keys are human readable alphanumeric strings. A parameter for the key
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`"ExampleParameter"` is stored under `[]byte("SubspaceName" + "/" + "ExampleParameter")`,
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where `"SubspaceName"` is the name of the subspace.
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Subkeys are secondary parameter keys those are used along with a primary parameter key.
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Subkeys can be used for grouping or dynamic parameter key generation during runtime.
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## KeyTable
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All of the parameter keys that will be used should be registered at the compile
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time. `KeyTable` is essentially a `map[string]attribute`, where the `string` is a parameter key.
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Currently, `attribute` consists of a `reflect.Type`, which indicates the parameter
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type to check that provided key and value are compatible and registered, as well as a function `ValueValidatorFn` to validate values.
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Only primary keys have to be registered on the `KeyTable`. Subkeys inherit the
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attribute of the primary key.
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## ParamSet
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Modules often define parameters as a proto message. The generated struct can implement
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`ParamSet` interface to be used with the following methods:
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* `KeyTable.RegisterParamSet()`: registers all parameters in the struct
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* `Subspace.{Get, Set}ParamSet()`: Get to & Set from the struct
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The implementor should be a pointer in order to use `GetParamSet()`.
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