Swift closures in autorelase pool accessing methods without self

问题

This is sample code

func anyMethod() {
    // Nothing here       
}
var myVariable = ""

autoreleasepool { 
   anyMethod() // This should show error
   print(myVariable) // This should show error

}

it should show error

Call to method 'anyMethod' in closure requires explicit 'self.' to make capture semantics explicit

But I am able to call anyMethod without self, I wonder why this not showing error

Why this is working without self ?

EDIT

Copy paste this class to re-produce

import Foundation
import UIKit

class AppGlobalManager:NSObject {
    var currentUserID:String?
    //Please ignore the method content as it is not the question
    func appendLog(string:String?) {
        print("LOG:",string)
    }


    func autoRelaseTest() {
        autoreleasepool {
            appendLog(string: "Any Log") // NO ERROR
        }
    }

    func normalFunctionTest () {
        normalFuncWithClosure {
            appendLog(string: "Test") //Call to method 'appendLog' in closure requires explicit 'self.' to make capture semantics explicit
        }
    }

    func normalFuncWithClosure (completion:@escaping() -> Void) {

        DispatchQueue.main.asyncAfter(deadline: .now() + 5) {
             completion()
        }


    }



}

回答1:

Calling an instance method or referencing an instance property in a closure requires explicit self if that closure is passed to a function taking an @escaping parameter. That makes it explicit that the self is possibly captured beyond the duration of the function call.

If the function parameter is not @escaping then no explicit self is required.

Here is a self-contained example:

func funcTakingNonescapingClosure(_ closure: () -> Void) { }
func funcTakingEscapingClosure(_ closure: @escaping () -> Void) { }

class Foo {

    func anyMethod() { }
    var myVariable = ""

    func test() {
        funcTakingNonescapingClosure {
            anyMethod() // No error
            print(myVariable) // No error
        }

        funcTakingEscapingClosure {
            anyMethod()
            // Call to method 'anyMethod' in closure requires explicit 'self.'
            // to make capture semantics explicit
            print(myVariable)
            // Reference to property 'myVariable' in closure requires explicit
            // 'self.' to make capture semantics explicit
        }
    }
}

In your example, Dispatch.main.async takes an escaping closure, but autorelease not.

来源：https://stackoverflow.com/questions/56443959/swift-closures-in-autorelase-pool-accessing-methods-without-self