Missing argument arrayLiteral in call

Question

I have a dictionary defined as:

var options: Dictionary <String, AnyObject>?

When I try to call

Array(options?.keys)

I get this error:

Missing argument label 'arrayLiteral:' in call

How do I get the keys out of my dictionary?

Answer 1

Object constructors (i.e. init()s) in Swift require a name for each argument, so you need to call Array(arrayLiteral: options?.keys). You probably have to unwrap the optional, though.

Answer 2

One answer is that you are passing it an optional value instead of a regular / non-optional value.

This works:

var options: Dictionary <String, AnyObject>?
Array(options!.keys)

There is more to this though. In a separate case of my own, I have seen this error when creating a set from a literal array of custom objects, but only after I changed the custom object to not inherit from NSObject.

The plot thickens.