Swift: Stuck with a compiler error - swift

Question

While exploring a structure read from a json file, I've got this message on the “if let” line which I'm stuck with:
'String' is not a subtype of '(String, AnyObject)'
The code is as follows:
if let descriptions: Array<Dictionary<String,AnyObject>> = fields["description"] as? Array {
let description = descriptions[0]
if let text:String = description["text"] as? String { // where the error occurs
poi.description = text
}
}

Answer 1

You have to unwrap what's read from the description dictionary:
if let text:String = description["text"]! as? String { // where the error occurs
...
}
But that's not safe, because if the key is not found in the dict, it throws a runtime exception. A safer way is:
if let text:String = (description["text"] as AnyObject?) as? String { // where the error occurs
...
}
However, I presume that you're using NSJSONSerialization to deserialize your json data, so a better way to do that is to stick with obj-c types rather than pure swift data types with generics:
if let descriptions = fields["description"] as? NSArray {
let description = descriptions[0] as NSDictionary
if let text = description["text"] as? String {
let x = text
}
}
More compact and much easier to read.

Answer 2

Use the new syntax and less of it.
Test declarations: Dictionary of Array of Dictionary
// let testFields: [String:[[String:Any]]]
or
// let testFields: [String:[[String:String]]]
let testFields = ["description":[["text":"value"]]]
if let descriptions = testFields["description"] {
let description = descriptions[0]
if let text = description["text"] as String? {
println("text: \(text)")
}
}
Output:
text: value