变量不是 class 的 static 成员

Question

I'm working on a GameKitHelper class, and it's mostly written in C++, but with Objective-C in some places as well, inside an.mm file.

I removed a bit of functionality to isolate the error:

void GameKitHelper::PopulateFriendScores(DynArray<GameCenterScore> *FriendScores)
{
    GKLeaderboard *leaderboardRequest = [[GKLeaderboard alloc] init];
    if (leaderboardRequest != nil)
    {
        leaderboardRequest.playerScope = GKLeaderboardPlayerScopeFriendsOnly;
        leaderboardRequest.timeScope = GKLeaderboardTimeScopeAllTime;
        leaderboardRequest.range = NSMakeRange(1,25);

        [leaderboardRequest loadScoresWithCompletionHandler: ^(NSArray *scores, NSError *error) 
         {
             int i = 0;
             printf("%d", i);
         }];
    }
}

The error I get here is:

'int GameKitHelper::i' is not a static member of 'class GameKitHelper'

Answer 1

This is a gcc bug. See Objective-C++ block vs Objective-C block for one of many reports of it.

<soapbox>I recommend avoiding Objective-C++ as much as possible. It's slow to compile, bloated to run (particularly with ARC since it turns on -fobjc-arc-exceptions ), buggy in the compiler and the debugger, and mostly a mess in my experience giving the worst of both worlds. C++ is fine. Objective-C is fine. Just keep the interface between them as small as possible. </soapbox>

But switching to clang 2.0 might fix this specific problem.

Answer 2

In case it might help someone else...

I am required by the needs of my project to use the 10.6 SDK and LLVM-gcc 4.2. I cannot require clang for the code to compile.

I worked around this problem by declaring my variable as a shared_ptr in the parent function... putting the actual object I need on the heap. In the block, I access the object through the shared_ptr variable. This arrangement causes the shared_ptr to be implicitly copied into the block while the copy in the parent function is free to be released. Since I am not declaring a variable in the block, I bypass the bug.

I used a preprocessor check to use a normal stack variable if the code is building on clang or some other compiler.