Capturing a struct reference in a closure doesn't allow mutations to occur

Question

I am trying to see if I can use structs for my model and was trying this. When I call vm.testClosure(), it does not change the value of x and I am

Answer 1

Instances of the closure will get their own, independent copy of the captured value that it, and only it, can alter. The value is captured in the time of executing the closure. Let see your slightly modified code

struct Model
{
    var x = 10.0

    mutating func modifyX(newValue: Double) {
        let this = self
        let model = m
        x = newValue
// put breakpoint here
//(lldb) po model
//▿ Model
//  - x : 30.0
//
//(lldb) po self
//▿ Model
//  - x : 301.0
//
//(lldb) po this
//▿ Model
//  - x : 30.0            
    }
}

var m = Model()

class ViewModel
{

    let testClosure:() -> ()

    init(inout model: Model)
    {
        model.x = 50
        testClosure =
            { () -> () in
                model.modifyX(301)
        }
        model.x = 30
    }
}

let mx = m.x

vm.testClosure()

let mx2 = m.x