Swift error when trying to access Dictionary: `Could not find member 'subscript'`

Question

This won\'t compile: I\'ve tried a couple different things; different ways of declaring th

Answer 1

response is declared as such:

var response = Dictionary<String,Any>()

So the compiler thinks response["current_rates"] will return an Any. Which may or may not be something that is subscript indexable.

You should be able to define you type with nested Dictionaries, 3 levels and eventually you get to a float. You also need to drill in with optional chaining since the dictionary may or may not have a value for that key, so it's subscript accessor returns an optional.

var response = Dictionary<String,Dictionary<String,Dictionary<String,Float>>>()
// ... populate dictionaries
println(response["current_rates"]?["a"]?["b"]) // The float

Answer 2

Let's take a look at

response["current_rates"][exchange][currency]

response is declared as Dictionary<String,Any>(), so after the first subscript you try to call another two subscripts on an object of type Any.

Solution 1. Change the type of response to be a nested dictionary. Note that I added the question marks because anytime you access a dictionary item you get back an optional.

var response = Dictionary<String,Dictionary<String,Dictionary<String, Float>>>()

func valueForCurrency(currency :String, exchange :String) -> Float? {
    return response["current_rates"]?[exchange]?[currency]
}

Solution 2. Cast each level to a Dictionary as you parse. Make sure to still check if optional values exist.

var response = Dictionary<String,Any>()

func valueForCurrency(currency :String, exchange :String) -> Float? {
    let exchanges = response["current_rates"] as? Dictionary<String,Any>

    let currencies = exchanges?[exchange] as? Dictionary<String,Any>

    return currencies?[currency] as? Float
}

Answer 3

You can get nested dictionary data by following these steps:

let imageData: NSDictionary = userInfo["picture"]?["data"]? as NSDictionary
let profilePic = imageData["url"] as? String

Answer 4

func valueForCurrency(currency :String, exchange :String) -> Float? {
    if let exchanges = response["current_rates"] as? Dictionary<String,Any> {
        if let currencies = exchanges[exchange] as? Dictionary<String,Any> {
            return currencies[currency] as? Float
        }
    }
    return nil
}