Question

所以我设置此方法来检索我的用户默认值。它应该检查密钥是否包含任何内容。如果没有，则返回nil。如果是，则返回该对象。很简单吧？无论如何，如果物体不存在，它会崩溃。它也没有通过这种方法。如果对象是nil，它将继续进入if语句ANYWAYS并在其评论的位置崩溃。我不明白为什么它继续进入if语句而不是跳到其他地方并继续前进。但是，如果对象存在于默认值中，则应用程序可以正常运行。任何想法？

+ (PAUserObject *)fetchDataSetWithDefaults {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    id data = [defaults objectForKey:kPAUserDefaultsStorage];

 // at ^^^ this point, data is nil (as it should be)

    NSLog(@"MY KEY - %@", data);
 // ^^^ Still (correctly) nil

    if([defaults objectForKey:kPAUserDefaultsStorage]){ // <--- This should return nil, since it printed as nil in the last 2 statements
        NSData *thisData = [[NSUserDefaults standardUserDefaults] objectForKey:kPAUserDefaultsStorage]; // <--- What the %$#@? it entered the if statement anyways?

        NSLog(@"Encoded Array - %@", thisData);
        PAUserObject *userObject = [NSKeyedUnarchiver unarchiveObjectWithData:thisData]; // <--- CRASH
        NSLog(@"decoding data");
        return userObject;
    } else { // <--- DOESNT EVEN REACH THIS CODE!!! WTF
        return nil;
    }
}

调试步骤

我放置了断点并检查了变量值，直到崩溃为止。就我所知，这绝对是它崩溃的路线

错误消息：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSArrayM insertObject:atIndex:]: object cannot be nil'

Answer 1

因此，您的错误很明显：您无法将nil对象传递给该函数。

但是，我复制了你的代码......并道歉，但它正常运作 ..

#define kPAUserDefaultsStorage @"key"

+ (NSString *)fetchDataSetWithDefaults {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    id data = [defaults objectForKey:kPAUserDefaultsStorage];

    // at ^^^ this point, data is nil (as it should be)

    NSLog(@"MY KEY - %@", data);
    // ^^^ Still (correctly) nil

    if([defaults objectForKey:kPAUserDefaultsStorage]){ // <--- This should return nil, since it printed as nil in the last 2 statements
        NSData *thisData = [[NSUserDefaults standardUserDefaults] objectForKey:kPAUserDefaultsStorage]; // <--- What the %$#@? it entered the if statement anyways?

        NSLog(@"Encoded Array - %@", thisData);
        // <--- CRASH
        NSLog(@"decoding data");

        return @"IS NOT NIL";
    } else { // <--- DOESNT EVEN REACH THIS CODE!!! WTF
        return @"IS NIL";
    }
}

从这里打来：

 NSLog(@"%@", [[self class] fetchDataSetWithDefaults]);

控制台日志：

2014-05-26 23:32:36.450 Test[11540:60b] MY KEY - (null)
2014-05-26 23:32:44.886 Test[11540:60b] IS NIL

获取NSUserDefaults对象时出错？

1 个答案: