Cannot range over type interface{}

[Buntu Dev]

Hi,

I'm a newbie and trying to understand how I can convert an argument of type interface {} back to a map so that I can iterate over the map.

Heres my sample code:

func SampleFunc(result interface{}) {

   // How to iterate over the result?

   // Below code gives "cannot range over result (type interface {})" error

   

    for k, v := range result {

           // do something

    }

}

func SomeOtherFunc() {

       tempMap := make(map[string]interface{})

       tempMap["aaa"] = "bbb"

       resultArray := make([]map[string]interface{}, 0)

       resultArray = append(result, rm)

       SampleFunc(resultArray)

}

How do I convert the interface back to the map array and iterate over the map to access the key-value pairs? 

Thanks for all the help!

[Buntu Dev]

There was a typo in the original message.. heres the sample code:

func SampleFunc(result interface{}) {

   // How to iterate over the result?

   // Below code gives "cannot range over result (type interface {})" error

   

    for k, v := range result {

           // do something

    }

}

func SomeOtherFunc() {

       tempMap := make(map[string]interface{})

       tempMap["aaa"] = "bbb"

       resultArray := make([]map[string]interface{}, 0)

       resultArray = append(resultArray, rm)

       SampleFunc(resultArray)

}

On Tuesday, January 14, 2014 4:59:07 PM UTC-8, Buntu Dev wrote:

Hi,

I'm a newbie and trying to understand how I can convert an argument of type interface {} back to a map so that I can iterate over the map.

Heres my sample code:

func SampleFunc(result interface{}) {

   // How to iterate over the result?

   // Below code gives "cannot range over result (type interface {})" error

   

    for k, v := range result {

           // do something

    }

}

func SomeOtherFunc() {

       tempMap := make(map[string]interface{})

       tempMap["aaa"] = "bbb"

       resultArray := make([]map[string]interface{}, 0)

       resultArray = append(resultArray, rm)

[Buntu Dev]

one more typo.. sorry:

func SampleFunc(result interface{}) {

   // How to iterate over the result?

   // Below code gives "cannot range over result (type interface {})" error

   

    for k, v := range result {

           // do something

    }

}

func SomeOtherFunc() {

       tempMap := make(map[string]interface{})

       tempMap["aaa"] = "bbb"

       resultArray := make([]map[string]interface{}, 0)

       resultArray = append(resultArray, tempMap)

       SampleFunc(resultArray)

[Andy Balholm]

Why are you passing the parameter as interface{} ?

[Jsor]

The most important question is: do you know the possible types of the map?

If so, use a type switch

switch myMap := result.(type) {

    case map[string]interface{}:

        // do stuff

    case map[int]string:

    // etc

}

If not, it gets trickier, and you have to use reflection. You'll want to take a look at reflect.ValueOf(); reflect.Value.Kind; reflect.Value.MapKeys; and reflect.Value.MapIndex.

[Buntu Dev]

Thanks Jsor for the response.. yes, I know the possible types. In the switch statement, does result get converted to a map and we can iterate over myMap? or is there any additional step to do the conversion?

[Jsor]

The myMap := result.(type) idiom in a switch statement declares myMap as a variable of the type triggered by the case, so in my example if

case map[string]interface{}

is triggered, then myMap will be a variable of type map[string]interface{}

[Buntu Dev]

Thanks Jsor, let me know if I'm over doing something:

 http://play.golang.org/p/wWoYlv7QBf