Context and ChainEnv

In Quick Start, we have seen how to customize an Writing, there are two parameters here, one is context, the other is ChainEnv, they represent two different the use of.

Context represents contextual information for interactions with off-chain. It includes caller address, passed parameters 、 event、error。

• The parameters passed in by the client caller (that is, the person who initiated the transaction) will be serialized in the form of json and stored in context in the form of string -> interface{} map. We use context to get the cryptographic address of the client caller and the parameters passed in by the caller. from context When getting parameters, you can use any go basic type to get parameters. If the parameter type is custom, you need to obtain interface through context.Get(paramName) and then convert it yourself. The types of parameters that can be directly obtained are:

   common.Hash([32]byte)
   common.Address([20]byte)
   string
   []byte
   bool 
   int, int8, int16, int32, int64
   uint, uint8, uint16, uint32, uint64
   float32, float64

• At the same time, if you need to return event out of the chain, you also need to complete it through context (ctx.EmitEvent([]byte)).

ChainEnv contains all environment components related to all chains, including blockchain, txdb, txpool, state, Execute, P2pNetwork. Components that can be directly manipulated by developers to the bottom layer of the framework.