[] map [string] string到csv [] byte的惯用转换

Question

I have a method which accepts an io.Reader in order to make an http POST (I can change this if needed) I will be submitted batches of x rows to this call method. I'm storing my rows as map[string]string for ease of checking that the keys are correct. What is the most streamlined way to submit a slice of map[string]string to that call method, which currently accepts a io.Reader?

Answer 1

Use the encoding/csv package to generate the CSV encoding. Here's how to encode to a []byte given column names:

func encodeCSV(columns []string, rows []map[string]string) ([]byte, error) {
    var buf bytes.Buffer
    w := csv.NewWriter(&buf)
    if err := w.Write(columns); err != nil {
       return nil, err
    }
    r := make([]string, len(columns))
    for _, row :=  range rows {
       for i, column := range columns {
         r[i] = row[column]
       }
       if err := w.Write(r); err != nil {
          return nil, err
       }
    }
    if err := w.Flush(); err != nil {
       return nil, err
    }
    return buf.Bytes(), nil
 }

Use bytes.NewReader to create the body for post:

data, err := encodeCSV(coluns, rows)
if err != nil {
   // handle error
}
req, err := http.NewRequest("POST", url, bytes.NewReader(data))

If you have control over the data format, then consider using JSON:

data, err := json.Marshal(rows)
if err != nil {
    // handle error
}
req, err := http.NewRequest("POST", url, bytes.NewReader(data))