在Objective-C中，可以向它们的类中添加一个描述方法以帮助调试：
@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？
