Swift的等价物是什么-[NSObject描述]？

Question

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

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

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

但我想重写此行为，以便打印到控制台：

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

是否有方法清理此println输出？我看过printable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 }
}

我认为println会自动“看到”这一点，但情况似乎并非如此：

  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)

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

Answer 1

要在Swift类型上实现此功能，必须实现CustomStringConvertable协议，然后实现名为Description的字符串属性。

例如：

class MyClass: CustomStringConvertible {
    let foo = 42

    var description: String {
        return "<\(type(of: self)): foo = \(foo)>"
    }
}

print(MyClass()) // prints: <MyClass: foo = 42>

注意:type(of:self)获取当前实例的类型，而不是显式地编写'MyClass'。