ios - 警告 : "Sending ' NSObject *' to parameter of incompatible type ' id'

Question

我被这个警告困扰了好几个小时......我越来越

代码是，

-(NSMutableDictionary*)iOSDiction
        {
            NSMutableDictionary *tmpDic = [[NSMutableDictionary alloc] initWithCapacity:[m_coordDic count]];
            for (NSObject *key in [m_coordDic allKeys]) 
            {
                [tmpDic setObject:[m_coordDic objectForKey:key] forKey:key];  //Warning
            }
            return tmpDic;
        }

警告:

"Sending 'NSObject *' to parameter of incompatible type 'id'

在这里将参数传递给参数aKey

NSDictionary.h

- (void)setObject:(id)anObject forKey:(id <NSCopying>)aKey;

Answer 1

NSDictionary 键应该符合 NSCopying 协议(protocol)。这是 NSDictionary 中指定的 key 的基本要求。引用。一般来说，NSObject 不符合协议(protocol)(它的子类可能)，因此您会收到警告。正确的做法是

NSMutableDictionary *tmpDic = [[NSMutableDictionary alloc] initWithCapacity:[m_coordDic count]];
for (NSObject<NSCopying> *key in [m_coordDic allKeys]) 
{
    [tmpDic setObject:[m_coordDic objectForKey:key] forKey:key];  //Warning
}
return tmpDic;

这确保您的 key 是确认 NSCopying 协议(protocol)的任何对象。

编辑:看来您真正想做的只是 [m_coordDic mutableCopy]，一个浅拷贝。您有什么理由不这样做？