Auto release pool and NSError

NSError Autorelease GG.m

#import <Foundation/Foundation.h>

// Assume -fobjc-arc ... 假設有 ARC
//
// 存成 `main.m` 然後在 Terminal 跑 `clang -framework Foundation -fobjc-arc -o main main.m && ./main && rm main`
// 然後在 `./main` 就會動囉
//

NSArray *ggFunction1(NSError *__autoreleasing *error) {
    @autoreleasepool {
        if (error) {
            *error = [NSError errorWithDomain:@"QQ domain" code:0 userInfo:nil];
        }
        return nil;
    }
}

NSArray *ggFunction2(NSError *__autoreleasing *error) {
    @autoreleasepool {
        if (error) {
            *error = [[NSError alloc] initWithDomain:@"QQ domain" code:0 userInfo:nil];
        }
        return nil;
    }
}

NSArray *okFunction(NSError *__autoreleasing *outError) {
    NSArray *result = nil;
    NSError *error = nil;
    @autoreleasepool {
        error = [[NSError alloc] initWithDomain:@"OK domain" code:0 userInfo:nil];
        result = nil;  // QQ
    }
    if (outError) {
        *outError = error;
    }
    return result;
}

int main(int argc, char *argv[]) {
    @autoreleasepool {
        NSLog(@"OK Start --------------");
        NSError *error1;
        NSArray *array1 = okFunction(&error1);
        NSLog(@"ok: %@: %@", array1, error1);
        NSLog(@"OK End   --------------");

        NSLog(@"GG1 Start --------------");
        NSError *error2;
        NSArray *array2 = ggFunction1(&error2);
        NSLog(@"gg: %@: %@", array2, error2);
        NSLog(@"GG1 End   --------------");

        NSLog(@"GG2 Start --------------");
        NSError *error3;
        NSArray *array3 = ggFunction2(&error3);
        NSLog(@"gg: %@: %@", array3, error3);
        NSLog(@"GG2 End   --------------");
    }
    return 0;
}