objective-c - 如何在带有 nil 终止参数列表的 init 方法中调用 super ？

Question

我正在继承 UIAlertView。我想实现一个具有以下签名的 init 方法:

- (id)initWithTitle:(NSString *)title 
            message:(NSString *)message
         identifier:(NSInteger)ident
           delegate:(id)delegate 
  cancelButtonTitle:(NSString *)cancelButtonTitle 
  otherButtonTitles:(NSString *)otherButtonTitles,...

它只是默认的 UIAlertView 方法，添加了参数 identifier。

- (id)initWithTitle:(NSString *)title 
            message:(NSString *)message
           delegate:(id)delegate 
  cancelButtonTitle:(NSString *)cancelButtonTitle 
  otherButtonTitles:(NSString *)otherButtonTitles,...

如果我在编译时不知道我的 init 方法 otherButtonTitles 参数是什么，现在调用 super 方法的正确语法是什么？

self = [super initWithTitle:title
                    message:message
                   delegate:delegate
          cancelButtonTitle:cancelButtonTitle 
          otherButtonTitles:otherButtonTitles, nil];
//I will only get the first param with this syntax

Answer 1

首先，了解一下可变参数函数，它可以帮助你:Wikipedia

Example:
#include <stdarg.h>

void logObjects(id firstObject, ...) // <-- there is always at least one arg, "nil", so this is valid, even for "empty" list
{
  va_list args;
  va_start(args, firstObject);
  id obj;
  for (obj = firstObject; obj != nil; obj = va_arg(args, id)) // we assume that all arguments are objects
    NSLog(@"%@", obj);
  va_end(args);
}

其次，最好创建一个 Objectve-C 类别，而不是 UIAlertView 的子类

Example:
@interface UIAlertView(Identifiers)
- (id)initWithTitle:(NSString *)title 
            message:(NSString *)message
         identifier:(NSInteger)ident
           delegate:(id)delegate 
  cancelButtonTitle:(NSString *)cancelButtonTitle 
  otherButtonTitles:(NSString *)otherButtonTitles,...;
@end