NSMutableDictionary中的对象突然变为空(Object in NSMutableDictionary suddenly becomes null)

 更新： 
 
 我添加了一个检查字典中的空对象的方法，事实上，他们被发现： 
 
 
 有没有人见过类似的东西？ 这不能由不正确的内存管理引起。 请注意，左侧的字典对象树实际上是正确的。 
 
 结束更新 
 
 我在启用ARC的情况下向NSMutableDictionary添加了一些条目。 添加其中一个之后，突然添加的对象变为空。 这里的代码（我扩大它，以确保我没有发疯）： 
 
NSMutableDictionary *base = [NSMutableDictionary dictionary];

id o = [GAConstant kTRUE];
id k = [GAClause parse:@"(x 1 1)"];
[base setObject:o forKey:k];
NSLog(@"### Added (%@ -> %@): %@", k, o, base);

o = [GAClause parse:@"(y X)"];
k = [GAClause parse:@"(x 2 X)"];
[base setObject:o forKey:k];
NSLog(@"### Added (%@ -> %@): %@", k, o, base);

o = [GAConstant kTRUE];
k = [GAClause parse:@"(y 3)"];
[base setObject:o forKey:k];
NSLog(@"### Added (%@ -> %@): %@", k, o, base);

o = [GAConstant kTRUE];
k = [GAClause parse:@"(y 6)"];
[base setObject:o forKey:k];
NSLog(@"### Added (%@ -> %@): %@", k, o, base);
 
 这是输出： 
 
2013-03-25 16:10:33.546 Jungle[1978:11303] ### Added (<GAListClause: 0x75b0dc0> -> <GAConstant: 0x75b12b0>): {
    "<GAListClause: 0x75b1b00>" = "<GAConstant: 0x75b12b0>";
}
2013-03-25 16:10:33.548 Jungle[1978:11303] ### Added (<GAListClause: 0x75b2870> -> <GAListClause: 0x75b1aa0>): {
    "<GAListClause: 0x75b2270>" = "<GAListClause: 0x75b1aa0>";
    "<GAListClause: 0x75b1b00>" = "<GAConstant: 0x75b12b0>";
}
2013-03-25 16:10:33.549 Jungle[1978:11303] ### Added (<GAListClause: 0x75b2b90> -> <GAConstant: 0x75b12b0>): {
    "<GAListClause: 0x75b2d80>" = "<GAConstant: 0x75b12b0>";
    "<GAListClause: 0x75b2270>" = "<GAListClause: 0x75b1aa0>";
    "<GAListClause: 0x75b1b00>" = "<GAConstant: 0x75b12b0>";
}
2013-03-25 16:10:33.550 Jungle[1978:11303] ### Added (<GAListClause: 0x75b2f00> -> <GAConstant: 0x75b12b0>): {
    "<GAListClause: 0x75b2d80>" = "<GAConstant: 0x75b12b0>";
    "<GAListClause: 0x75b2270>" = "<GAListClause: 0x75b1aa0>";
    "<GAListClause: 0x75b1b00>" = "<GAConstant: 0x75b12b0>";
    "<GAListClause: 0x75b1d60>" = (null);
}
 
 方法[GAConstant kTRUE]初始化并返回一个静态变量。 [GAClause parse:]每次都会返回一个新的解析对象。 
 
 很明显，为什么k变量的地址不符合字典的内容：它会复制它们。 仍然不清楚null是如何潜入其中的。 字典中null的位置会随着每次运行而改变，有时我会得到其中的两个。 
 
 看起来内存管理正在发生，但是什么？ ARC在此处启用。 
 
 以下是与[GAConstant kTRUE]方法相关的代码： 
 
+ (GAConstant *)kTRUE {
    static GAConstant *kTRUE = nil;
    static dispatch_once_t onceToken = 0;

    dispatch_once(&onceToken, ^{
        kTRUE = [[GAConstant alloc] initWithString:@"true"];
    });

    return kTRUE;
}
 
 有时零字在字典中波动： 
 
2013-03-25 17:09:16.426 Jungle[2294:11303] ### Added (<GAListClause: 0x7182ce0> -> <GAConstant: 0x7183430>): {
    "<GAListClause: 0x7183a30>" = "<GAConstant: 0x7183430>";
}
2013-03-25 17:09:16.428 Jungle[2294:11303] ### Added (<GAListClause: 0x75467b0> -> <GAListClause: 0x71839d0>): {
    "<GAListClause: 0x7546a30>" = (null);
    "<GAListClause: 0x7183a30>" = "<GAConstant: 0x7183430>";
}
2013-03-25 17:09:16.429 Jungle[2294:11303] ### Added (<GAListClause: 0x7546cd0> -> <GAConstant: 0x7183430>): {
    "<GAListClause: 0x7546ec0>" = "<GAConstant: 0x7183430>";
    "<GAListClause: 0x7546a30>" = "<GAListClause: 0x71839d0>";
    "<GAListClause: 0x7183a30>" = "<GAConstant: 0x7183430>";
}
2013-03-25 17:09:16.430 Jungle[2294:11303] ### Added (<GAListClause: 0x7547040> -> <GAConstant: 0x7183430>): {
    "<GAListClause: 0x75470f0>" = (null);
    "<GAListClause: 0x7546ec0>" = "<GAConstant: 0x7183430>";
    "<GAListClause: 0x7546a30>" = "<GAListClause: 0x71839d0>";
    "<GAListClause: 0x7183a30>" = "<GAConstant: 0x7183430>";
}
 
 以下是它在调试器中的样子： 
 

Update:
 
I have added a method that checks for null objects in dictionary and indeed, they were found:
 
 
Did anyone ever seen anything like this? This can't be caused by incorrect memory management. Note that dictionary object tree on the left is actually correct.
 
End update
 
I'm adding a number of entries to the NSMutableDictionary with ARC enabled. After one of the additions the object added suddenly becomes null. Here's the code (I expanded it to make sure I haven't gone mad):
 
NSMutableDictionary *base = [NSMutableDictionary dictionary];

id o = [GAConstant kTRUE];
id k = [GAClause parse:@"(x 1 1)"];
[base setObject:o forKey:k];
NSLog(@"### Added (%@ -> %@): %@", k, o, base);

o = [GAClause parse:@"(y X)"];
k = [GAClause parse:@"(x 2 X)"];
[base setObject:o forKey:k];
NSLog(@"### Added (%@ -> %@): %@", k, o, base);

o = [GAConstant kTRUE];
k = [GAClause parse:@"(y 3)"];
[base setObject:o forKey:k];
NSLog(@"### Added (%@ -> %@): %@", k, o, base);

o = [GAConstant kTRUE];
k = [GAClause parse:@"(y 6)"];
[base setObject:o forKey:k];
NSLog(@"### Added (%@ -> %@): %@", k, o, base);
 
Here's the output:
 
2013-03-25 16:10:33.546 Jungle[1978:11303] ### Added (<GAListClause: 0x75b0dc0> -> <GAConstant: 0x75b12b0>): {
    "<GAListClause: 0x75b1b00>" = "<GAConstant: 0x75b12b0>";
}
2013-03-25 16:10:33.548 Jungle[1978:11303] ### Added (<GAListClause: 0x75b2870> -> <GAListClause: 0x75b1aa0>): {
    "<GAListClause: 0x75b2270>" = "<GAListClause: 0x75b1aa0>";
    "<GAListClause: 0x75b1b00>" = "<GAConstant: 0x75b12b0>";
}
2013-03-25 16:10:33.549 Jungle[1978:11303] ### Added (<GAListClause: 0x75b2b90> -> <GAConstant: 0x75b12b0>): {
    "<GAListClause: 0x75b2d80>" = "<GAConstant: 0x75b12b0>";
    "<GAListClause: 0x75b2270>" = "<GAListClause: 0x75b1aa0>";
    "<GAListClause: 0x75b1b00>" = "<GAConstant: 0x75b12b0>";
}
2013-03-25 16:10:33.550 Jungle[1978:11303] ### Added (<GAListClause: 0x75b2f00> -> <GAConstant: 0x75b12b0>): {
    "<GAListClause: 0x75b2d80>" = "<GAConstant: 0x75b12b0>";
    "<GAListClause: 0x75b2270>" = "<GAListClause: 0x75b1aa0>";
    "<GAListClause: 0x75b1b00>" = "<GAConstant: 0x75b12b0>";
    "<GAListClause: 0x75b1d60>" = (null);
}
 
The method [GAConstant kTRUE] initializes and returns a static variable. [GAClause parse:] returns a new parsed object every time.
 
It's clear why addresses of k variables do not correspond to the contents of the dictionary: it copies them. Still not clear how a null can sneak in as a value. The location of null in the dictionary changes with every run, sometimes I'm getting two of them.
 
Looks like something is going on with the memory management, but what? ARC is enabled here.
 
Here's the code relevant to [GAConstant kTRUE] method:
 
+ (GAConstant *)kTRUE {
    static GAConstant *kTRUE = nil;
    static dispatch_once_t onceToken = 0;

    dispatch_once(&onceToken, ^{
        kTRUE = [[GAConstant alloc] initWithString:@"true"];
    });

    return kTRUE;
}
 
Sometimes null is fluctuating across the dictionary:
 
2013-03-25 17:09:16.426 Jungle[2294:11303] ### Added (<GAListClause: 0x7182ce0> -> <GAConstant: 0x7183430>): {
    "<GAListClause: 0x7183a30>" = "<GAConstant: 0x7183430>";
}
2013-03-25 17:09:16.428 Jungle[2294:11303] ### Added (<GAListClause: 0x75467b0> -> <GAListClause: 0x71839d0>): {
    "<GAListClause: 0x7546a30>" = (null);
    "<GAListClause: 0x7183a30>" = "<GAConstant: 0x7183430>";
}
2013-03-25 17:09:16.429 Jungle[2294:11303] ### Added (<GAListClause: 0x7546cd0> -> <GAConstant: 0x7183430>): {
    "<GAListClause: 0x7546ec0>" = "<GAConstant: 0x7183430>";
    "<GAListClause: 0x7546a30>" = "<GAListClause: 0x71839d0>";
    "<GAListClause: 0x7183a30>" = "<GAConstant: 0x7183430>";
}
2013-03-25 17:09:16.430 Jungle[2294:11303] ### Added (<GAListClause: 0x7547040> -> <GAConstant: 0x7183430>): {
    "<GAListClause: 0x75470f0>" = (null);
    "<GAListClause: 0x7546ec0>" = "<GAConstant: 0x7183430>";
    "<GAListClause: 0x7546a30>" = "<GAListClause: 0x71839d0>";
    "<GAListClause: 0x7183a30>" = "<GAConstant: 0x7183430>";
}
 
Here's what it looks like in the debugger:
 

原文：https://stackoverflow.com/questions/15620084