NewAppModule creates a new AppModule Object.

NewHandler本质上是一个子路由，它将进入该模块的msg路由到正确的handler做处理。 NewHandler returns a handler for "nameservice" type messages.

Keeper的构造函数 NewKeeper creates new instances of the nameservice Keeper.

该函数充当查询此模块的子路由器 因为querier没有类似于Msg的接口，所以需要手动定义switch语句（它们无法从query.Route()函数中删除） NewQuerier is the module level router for state queries.

query endpoints supported by the nameservice Querier.

传入一个域名返回nameservice给定的解析值。类似于DNS查询。.

传入一个域名返回价格，解析值和域名的所有者。用于确定你想要购买名称的成本。.

app module Basics object.

Keeper maintains the link to data storage and exposes getter/setter methods for the various parts of the state machine.