什么是Swift等价的 – [NSObject description]？

@implementation MyClass
- (NSString *)description
{
    return [NSString stringWithFormat:@"<%@: %p,foo = %@>",[self class],foo _foo];
}
@end

然后在调试器中，您可以：

po fooClass
<MyClass: 0x12938004,foo = "bar">

Swift中的等价物是什么？ Swift的REPL输出可能有帮助：

1> class MyClass { let foo = 42 }
  2> 
  3> let x = MyClass()
x: MyClass = {
  foo = 42
}

但我想覆盖这种行为打印到控制台：

4> println("x = (x)")
x = C11lldb_expr_07MyClass (has 1 child)

有没有办法清理这个println输出？我看过可打印协议：

/// This protocol should be adopted by types that wish to customize their
/// textual representation.  This textual representation is used when objects
/// are written to an `OutputStream`.
protocol Printable {
    var description: String { get }
}

我想这将自动被“看到”println，但似乎不是这样的情况：

1> class MyClass: Printable {
  2.     let foo = 42
  3.     var description: String { get { return "MyClass,foo = (foo)" } }
  4. }   
  5> 
  6> let x = MyClass()
x: MyClass = {
  foo = 42
}
  7> println("x = (x)")
x = C11lldb_expr_07MyClass (has 1 child)

而我必须显式调用description：

8> println("x = (x.description)")
x = MyClass,foo = 42

有没有更好的办法？