警告：“将‘NSObject *’发送到不兼容类型‘id<NSCopying>’的参数

Question

我在这个警告中震惊了好几个小时......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 ：

“将‘NSObject *’发送到不兼容类型‘id’的参数

aKey在此处将参数传递给参数

NSDictionary.h

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

Answer 1

NSDictionary密钥应符合NSCopying协议。这是NSDictionary参考中指定的密钥的基本要求。一般来说，NSObject不符合协议（它的子类可能），所以你会收到警告。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;

这确保您的密钥是任何确认NSCopying协议的对象。

编辑：看来你真正想做的只是[m_coordDic mutableCopy]一个浅拷贝。你有什么理由不这样做？