Several disappointing Swift code snippets...

example1.swift

class MyClass {
  var someValue:Int
  func someMethod() -> Int {
    return 42
  }
  
  var callback:(Int) -> (Void) = {(value:Int) -> (Void) in
    // Using self within a closure owned by self makes reference loop
    self.someValue = self.someMethod() + value
  }
}

example2.swift

class MyClass {
  var someValue:Int
  func someMethod() -> Int {
    return 42
  }
  
  var callback:(Int) -> (Void) = {[unowned self] (value:Int) -> (Void) in
    // self is specified as unowned in closure capture list [unowned self],
    // so the following self is now unowned by this closure!
    self.someValue = self.someMethod() + value
    // By the way, cannot directly use variables and methods without self
    // (the following code is compiler error)
    /*
    someValue = someMethod() + value
    */
  }
}