注意：x/params 自 Cosmos SDK v0.53 起已弃用，并将在下一次发布中移除。

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摘要

params 包提供了一个全局可用的参数存储。 主要有两种类型：Keeper 和 Subspace。Subspace 是 paramstore 的隔离命名空间，其中键会带有预先配置的空间名称前缀。Keeper 具有访问所有现有空间的权限。 Subspace 可供各个 keeper 使用，以便它们拥有一个其他 keeper 无法修改的私有参数存储。params 的 Keeper 可用于向 x/gov 路由器添加一条路由，从而在提案通过时修改任意参数。 以下内容说明如何在主模块和用户模块中使用 params 模块。

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目录

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Keeper

在应用初始化阶段，可以使用 Keeper.Subspace 为其他模块的 keeper 分配 subspaces，并将其存储在 Keeper.spaces 中。随后，这些模块可以通过 Keeper.GetSubspace 获取各自特定参数存储的引用。 示例： 
type ExampleKeeper struct {
    paramSpace paramtypes.Subspace
}

func (k ExampleKeeper)

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

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Subspace

Subspace 是参数存储的一个带前缀的子空间。每个使用参数存储的模块都会使用一个 Subspace，以隔离访问权限。

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Key

参数键是人类可读的字母数字字符串。键 "ExampleParameter" 对应的参数会存储在 []byte("SubspaceName" + "/" + "ExampleParameter") 下，其中 "SubspaceName" 是该子空间的名称。 子键是与主参数键配合使用的次级参数键。子键可用于分组，或在运行时动态生成参数键。

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KeyTable

所有将要使用的参数键都应在编译期完成注册。KeyTable 本质上是一个 map[string]attribute，其中 string 是参数键。 目前，attribute 由一个 reflect.Type 组成，它用于指示参数类型，以检查给定的键和值是否兼容且已注册，同时还包含一个用于校验值的函数 ValueValidatorFn。 只有主键需要注册到 KeyTable 中。子键会继承主键的 attribute。

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ParamSet

模块通常将参数定义为一个 proto message。生成的结构体可以实现 ParamSet 接口，以配合以下方法使用：
  • KeyTable.RegisterParamSet()：注册结构体中的所有参数
  • Subspace.{Get, Set}ParamSet()：从结构体中获取参数并设置回结构体
实现者应为指针类型，以便使用 GetParamSet()。
NOTE: x/params is deprecated as of Cosmos SDK v0.53 and will be removed in the next release.

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Abstract

Package params provides a globally available parameter store. There are two main types, Keeper and Subspace. Subspace is an isolated namespace for a paramstore, where keys are prefixed by preconfigured spacename. Keeper has a permission to access all existing spaces. Subspace can be used by the individual keepers, which need a private parameter store 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. The following contents explains how to use params module for master and user modules.

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Contents

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Keeper

In the app initialization stage, subspaces 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. Example: 
type ExampleKeeper struct {
    paramSpace paramtypes.Subspace
}

func (k ExampleKeeper)

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

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Subspace

Subspace is a prefixed subspace of the parameter store. Each module which uses the parameter store will take a Subspace to isolate permission to access.

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Key

Parameter keys are human readable alphanumeric strings. A parameter for the key "ExampleParameter" is stored under []byte("SubspaceName" + "/" + "ExampleParameter"), where "SubspaceName" is the name of the subspace. Subkeys are secondary parameter keys those are used along with a primary parameter key. Subkeys can be used for grouping or dynamic parameter key generation during runtime.

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KeyTable

All of the parameter keys that will be used should be registered at the compile time. KeyTable is essentially a map[string]attribute, where the string is a parameter key. Currently, attribute consists of a reflect.Type, which indicates the parameter type to check that provided key and value are compatible and registered, as well as a function ValueValidatorFn to validate values. Only primary keys have to be registered on the KeyTable. Subkeys inherit the attribute of the primary key.

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ParamSet

Modules often define parameters as a proto message. The generated struct can implement ParamSet interface to be used with the following methods:
  • KeyTable.RegisterParamSet(): registers all parameters in the struct
  • Subspace.{Get, Set}ParamSet(): Get to & Set from the struct
The implementor should be a pointer in order to use GetParamSet().