map with string key and string or slice value?

Question

Newbee warning.

Can I make a map with a string key and "anything" as a value? The goal is to have a map of configuration data. This data can be either a single string (or boolean value or integer, but restricting this to a string is fine), or it can be an array of strings. Example: I'd like to store these items:

levels = 3
extra-directories = ["foo","bar","baz"]

The first option is always a single value (a string would be OK for me). The second option is zero or more values.

The goal is to have a single map where I can store these values and when looking at the map, I could use switch x.(type) to find out what the value is.

Zippo · Accepted Answer · 2012-08-03 19:44:09Z

4

interface{} is a type that accepts any type.

conf := map[string] interface{} {
    "name": "Default",
    "server": "localhost",
    "timeout": 120,
}

conf["name"] is an interface{} not a string, and conf["timeout"] is an interface{} not an int. You can pass conf["name"] to functions that take interface{} like fmt.Println, but you can't pass it to functions that take string like strings.ToUpper, unless you know that the interface{}'s value is a string (which you do) and assert it's type:

name := conf["name"].(string)
fmt.Println("name:", strings.ToUpper(name))
server := conf["server"].(string)
fmt.Println("server:", strings.ToUpper(server))
timeout := conf["timeout"].(int)
fmt.Println("timeout in minutes:",  timeout / 60)

Another solution that might fit your problem is to define a struct:

type Config struct {
    Name string
    Server string
    Timeout int
}

Create configuration:

conf := Config{
    Name: "Default",
    Server: "localhost",
    Tiemout: 60,
}

Access configuration:

fmt.Println("name:", strings.ToUpper(conf.Name))
fmt.Println("server:", strings.ToUpper(cnf.Server))
fmt.Println("timeout in minutes:",  conf.Timeout / 60)

answered Aug 3, 2012 at 19:44

Zippo

16.5k11 gold badges62 silver badges58 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Jeremy Wall Over a year ago

Technically interface{} is an Interface that all types implement. It's a subtle distinction but worth mentioning.

zzzz · Accepted Answer · 2012-08-03 19:00:08Z

1

Yes, you can do that using a map having type map[string]interface{}.

answered Aug 3, 2012 at 19:00

zzzz

92k17 gold badges184 silver badges140 bronze badges

Collectives™ on Stack Overflow

map with string key and string or slice value?

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related