Cocoa Touch：访问器方法+内存需要说明

Question

请考虑构造数组并将其返回给父对象的问题。请看下面的代码和评论。

我的问题是：为什么方法THREE工作，而方法ONE和TWO不工作？

// **************************** 
// Master.m 
// **************************** 

// Simply declare array and call accessor 
NSMutableArray * allElementTypes; 
allElementTypes = [ElementObject badElements]; 




// **************************** 
// ElementObject.m 
// **************************** 

// Doesn't work (EXE_BAD_ACCESS) 
+ (NSMutableArray*) badElements { 
    NSMutableArray * array = [[NSMutableArray alloc] initWithObjects:@"crab", @"poison", @"snake"]; 
    return array; 
} 

// Doesn't work (EXE_BAD_ACCESS) 
+ (NSMutableArray*) badElements { 
    return [NSMutableArray arrayWithObjects:@"crab", @"poison", @"snake"]; 
} 

// WORKS 
+ (NSMutableArray*) badElements { 
    NSMutableArray * array = [[NSMutableArray alloc] init]; 
     [array addObject:@"crab"]; 
     [array addObject:@"poison"]; 
     [array addObject:@"snake"]; 

    return array; // TODO: release this memory 
} 

Answer 1

-arrayWithObjects：或-initWithObjects需要终止的零，可变长度，的参数列表。

您写道：

[NSMutableArray arrayWithObjects:@"crab", @"poison", @"snake"];

，你应该写：

[NSMutableArray arrayWithObjects:@"crab", @"poison", @"snake", nil];