Swift2 reflection help. Convert the value I get (type Any?) to Bool or Bool? accordingly

问题

for a unit test of mine, I wrote a small helper that can get me a property Value by name.

let m = Mirror(reflecting: self)
let child1 = m.descendant(name)

now the problem is that the child has Type Any? but the properties real type is e.g. Bool? So Any is actually an Optional!

Thats why if child1 is Bool? never fires because Any? isn't the Bool?.
But child1! is Bool? doesn't compile.
And child1! is Bool isn't true!

So how do I 'unbox' this reflected Any? value?

a small example of what I mean

import UIKit

class ViewController: UIViewController {
    let name = "asd"
    let boolvalue: Bool = true
    var optboolvalue: Bool? = true

    override func viewDidLoad() {
        print( getNumberForBool("boolvalue") )
        print( getNumberForBool("optboolvalue") )
    }

    func getNumberForBool( name: String ) -> NSNumber {
        let m = Mirror(reflecting: self)
        let child1 = m.descendant(name)

        if(child1 != nil) {
            //! only works for bool, not for bool?
            if let b = child1  as? Bool {
                return NSNumber(bool: b)
            }
            //this would be my interpretation of how to do it ... unwrap the any and unwrap it again. this doesn't compile though :)
//            if let b = child1! as! Bool? {
//                return NSNumber(bool: b!)
//            }
        }

        return NSNumber(bool: false)
    }
}

NOTE

The type of child1 for the case Bool?:

▿ Optional(Optional(true)) ▿ Some : Optional(true) - Some : true

回答1:

solution

I worked around the issue of not being able to cast an to Bool? by using reflection again

        if let any = child1, let maybeB = Mirror(reflecting: any).descendant("Some") as? Bool {
            if let b = (maybeB as Bool?) {
                return NSNumber(bool: b)
            }
        }

reflection ^ 2 :D

the complete gist:

https://gist.github.com/Daij-Djan/18e8ab9bcbaa3f073523

回答2:

the ?? operator unwraps the optional in case there is Some inside. If there is not, the value that is passed after eg. let foo = someOptional ?? alternativeValue.

This would give you an unwrapped Any. Since Swift is strongly typed you will only be getting the Bool if you would cast.

if let b = child, let c = b as? Bool {
       return NSNumber(bool: c)
}

来源：https://stackoverflow.com/questions/33707460/swift2-reflection-help-convert-the-value-i-get-type-any-to-bool-or-bool-acc

标签

reflection

swift2