CODEWITHSUNDEEP
swift
bolerovt
bolerovt

Reputation: 623

swift: what's type "(AnyObject)"?

I'm running into a very interesting error message today:

Cannot invoke 'map' with an argument list of type '(AnyObject)'

I don't even know there is an type in Swift called (AnyObject)!

the context is, I'm using a closure as a callback after an http request:

dataHandler: ((AnyObject) -> ())?,

and trying to get implement the dataHandler in this piece of code:

dataHandler: { (obj: AnyObject) -> () in ...}

at this moment, swift take "obj" as type: (Anyobject)...

Thanks for @sketchyTech's inspiring answer, ObjectMapper seems need concrete type of "AnyObject", like cast it into Array or Dictionary. Now my code works:

    if let dic = res as? [String: AnyObject], res = Mapper<MappableType>().map(dic) {
        ...
    }

Upvotes: 0

Views: 261

Answers (1)

sketchyTech
sketchyTech

Reputation: 5906

When used as a concrete type, rather than a generic type, AnyObject enables you to call any ObjC method (but of course it must be able to respond to the method at runtime to avoid crashing).

When used as a concrete type, all known @objc methods and properties are available, as implicitly-unwrapped-optional methods and properties respectively, on each instance of AnyObject. (Swift header file)

Its primary role is to help with passing objects between ObjC and the strongly-typed language of Swift.

For an instance of type AnyObject to be used with higher order Swift functions it must first be cast to a type to which they can be applied, e.g.

dataHandler: {arr in
    if let a = arr as? [Int] {
        a.map{$0+1}
    }}

Upvotes: 2

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