Golang将地图键设置为其值的变量

Question

I need to go through an html forms input values and place them into an mysql datbase. Which I'm currently using r.Form to get a map. So that i don't have to use r.Form.Get("date") for each which works but when i try to put the values into a database. It compiles just fine but i get sql: converting argument #0's type: unsupported type []string, a slice after i click submit in the browser. I can get around this by doing

`date := strings.Join(m["date"], "")`

but doing that for 30+ values especially since some of the submited values will be created from previous database entries using html templates. If i have to change or add more later seems like there must be a more efficient way I've seen for key, val := range m {} but unfortunately I've only been doing this for about a week and i can't figure out how to keep the values and change the variable they get set to after each iteration. So that after

for key, val := range m {
x := m[key]
}

so that it will put out the equivalent

keyname := keyvalue

changing the keyname each time to be the same as the keyname in the map ie

date := 2015-8-13
time := 18:56:11

or if there's an easier way around this error then to create a varible for each one.

Answer 1

An HTML form can have multiple values for a single key. This is why the request form field is defined to be a map of string slices. The request Form is declared as

 Form url.Values

and url.Values is declared as

  type Values map[string][]string

You can access the first value for a key using:

   var value string
   if values := req.Form[key]; len(values) > 0 {
      value = values[0]
   }

The url.Values Get helper method simplifies this code to:

   value := req.Form.Get(key)

The http.Request FormValue helper method simplifies it a bit more:

  value := req.FormValue(key)

You iterate through keys and values using:

  for key, values := range req.Form {
     for _, value := range values {
         fmt.Println(key, value)
     }
  }

If you want to iterate over the first value for a key, then use this code:

 for key, values := range req.Form {
    if len(values) > 0 {
       value := values[0]
       fmt.Println(key, value)
    }
 }

Before accessing req.Form, call req.ParseForm to parse the query string and request body.