flutter 对一个对象进行fromjson,tojson,encode和decode

fromJson就是转成我们能app能用的数据，tojson就是转成服务器能用的数据，
encode是列表/对象转json，decode是json转列表/对象

存在下面的一个对象

    RedEnvelopeModel redEnvelopeModel=RedEnvelopeModel(
      id: 1,
      mess: "1",
      owner: Owner(userId: "1",nickname: "1"),
      qty: "1",
      roomId: "102",
      topCoin: 1,
      totalCoin: "1",
      totalQty: "1"
    );

进行tojson得到 Map类型，服务器可用的数据类型：redEnvelopeModel.toJson()

{id: 1, mess: 1, owner: {nickname: 1, userId: 1}, qty: 1, roomId: 102, topCoin: 1, totalCoin: 1, totalQty: 1}

进行encode得到String类型，可以传String类型了：json.encode(redEnvelopeModel.toJson())

{"id":1,"mess":"1","owner":{"nickname":"1","userId":"1"},"qty":"1","roomId":"102","topCoin":1,"totalCoin":"1","totalQty":"1"}

前面如果用json.encode转过了，这边就用json.decode转回来
进行decode得到，将encode的String类型转成我们可以用的：json.decode(body)
RedEnvelopeModel model = RedEnvelopeModel.fromJson(json.decode(body));//fromJson之后就可以用了

{id: 1, mess: 1, owner: {nickname: 1, userId: 1}, qty: 1, roomId: 102, topCoin: 1, totalCoin: 1, totalQty: 1}