如何遍历解码器？

Question

I come from a Python background and so have a tendency to think in terms of iterators. It seems to me that the range keyword in Go intends for us to think in a nearly identical way, so I would like to do somthing semantically equivalent to this Python code in Go:

for obj in json_decoder:
    # business logic

Here is the motivating case in Go; consider the following function:

func (c *GorpController) Create(dec *json.Decoder) {
    // business logic
}

I would like to be able to implement it as:

for someValue := range dec {
    // business logic
}

Is there some sort of way to use range with a Decoder interface? A function that wraps it in a different interface would be ideal, and an idiomatic pattern would be acceptable.

Thank you!

Answer 1

Unfortunately, you can only use range with an "array, slice, string, or map, or reading from a channel" (see effective go)

to iterate over structs as they get decoded, the documentation recommends doing:

dec := json.NewDecoder(strings.NewReader(jsonStream))
for {
    var m Message
    if err := dec.Decode(&m); err == io.EOF {
        break
    } else if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("%s: %s
", m.Name, m.Text)
}

(taken directly from the official doc example)