将JSON解组为Golang类型Big.Float

Question

I have a json message that needs to be unmarshaled to a struct which has some big.Float fields from the math package. The json field is of type numeric. It gives me err = json: cannot unmarshal string into Go value of type *big.Float.

I wonder why it complains "cannot unmarshal string" since my json field is numeric type. And what do I need to do to unmarshal the json filed to a *big.Float field.

Example:

type Msg struct {  
      Usage0   *big.Float 
      Usage1   *big.Float 
      Usage2   *big.Float       
}

// jsonMsg = {'Usage0': 31241.4543, "Usage1": 54354325423.65, ...}

err := json.Unmarshal(jsonMsg, &msg)

Answer 1

It appears to me (based on the docs) that it expects the json for big.Float to be passed in as strings. This play proves that to work:

https://play.golang.org/p/7XKn2hhXRD

If you cannot control the json then you can implement your own unmarshaller as an alternative.