快速枚举使用NSMutableArray保存NSDictionary [英] Fast Enumeration With an NSMutableArray that holds an NSDictionary

问题描述

是否可以对包含NSDictionary的NSArray使用快速枚举？

我正在运行一些Objective C教程，下面的代码踢控制台进入GDB模式

  NSMutableArray * myObjects = [NSMutableArray array]; 
 NSArray * theObjects = [NSArray arrayWithObjects：@easy as 1，@easy as two，@Easy as Three]; 
 NSArray * theKeys = [NSArray arrayWithObjects：@A，@B，@C]; 
 NSDictionary * theDict = [NSDictionary dictionaryWithObjects：theObjects forKeys：theKeys]; 
 [myObjects addObject：theDict]; 
 
（myObjects中的id项）
 {
 NSLog（@找到一个项目：％@，item）; 
} 
  

如果我用传统的计数循环代替快速枚举循环

  int count = [myObjects count]; 
 for（int i = 0; i  {
 id item; 
 item = [myObjects objectAtIndex：i]; 
 NSLog（@Found an Item：％@，item）; 
} 
  

应用程序运行时没有崩溃，字典输出到控制台窗口。

这是Fast Enumeration的限制，还是我缺少一些细微的语言？当嵌套这样的集合时还有其他问题吗？

对于奖励积分，我如何使用GDB自己调试？

解决方案

糟糕！ arrayWithObjects：需要nil终止。以下代码运行正常：

  NSMutableArray * myObjects = [NSMutableArray array]; 
 NSArray * theObjects = [NSArray arrayWithObjects：@easy as 1，@easy as two，@Easy as Three，nil]; 
 NSArray * theKeys = [NSArray arrayWithObjects：@A，@B，@C，nil]; 
 NSDictionary * theDict = [NSDictionary dictionaryWithObjects：theObjects forKeys：theKeys]; 
 [myObjects addObject：theDict]; 
 
（myObjects中的id项）
 {
 NSLog（@找到一个项目：％@，item）; 
} 
  

我不知道为什么使用传统的循环会隐藏这个错误。 p>

Is it possible to use fast enumeration with an NSArray that contains an NSDictionary?

I'm running through some Objective C tutorials, and the following code kicks the console into GDB mode

NSMutableArray *myObjects = [NSMutableArray array];
NSArray *theObjects = [NSArray arrayWithObjects:@"easy as 1",@"easy as two", @"Easy as Three"];
NSArray *theKeys    = [NSArray arrayWithObjects:@"A",@"B",@"C"];    
NSDictionary *theDict = [NSDictionary dictionaryWithObjects:theObjects forKeys:theKeys];
[myObjects addObject:theDict];

for(id item in myObjects)
{
    NSLog(@"Found an Item: %@",item);
}

If I replace the fast enumeration loop with a traditional counting loop

int count = [myObjects count];
for(int i=0;i<count;i++)
{
    id item;
    item = [myObjects objectAtIndex:i];
    NSLog(@"Found an Item: %@",item);
}

The application runs without a crash, and the dictionary is output to the console window.

Is this a limitation of Fast Enumeration, or am I missing some subtly of the language? Are there other gotchas when nesting collections like this?

For bonus points, how could I used GDB to debug this myself?

解决方案

Oops! arrayWithObjects: needs to be nil-terminated. The following code runs just fine:

NSMutableArray *myObjects = [NSMutableArray array];
NSArray *theObjects = [NSArray arrayWithObjects:@"easy as 1",@"easy as two", @"Easy as Three",nil];
NSArray *theKeys    = [NSArray arrayWithObjects:@"A",@"B",@"C",nil];    
NSDictionary *theDict = [NSDictionary dictionaryWithObjects:theObjects forKeys:theKeys];
[myObjects addObject:theDict];

for(id item in myObjects)
{
    NSLog(@"Found an Item: %@",item);
}

I'm not sure why using a traditional loop hid this error.

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