保留合成属性的计数

@interface ClassA : NSObject {
    ClassB *objB;
}

@property (retain) ClassB *objB;
@end

@implementation ClassA:
@synthesiaze objB;
@end

int Main(int argc, const char *argv[])
{
    ClassA *objA = [[ClassA alloc] init];
    ClassB *objB = [[ClassB alloc] init];

    NSLog(@\"%d\", (int)[objB retainCount]);    // 1
    NSLog(@\"%d\", (int)[[objA objB] retainCount]);     // 0

    objA.objB = objB;

    NSLog(@\"%d\", (int)[objB retainCount]);    // 2
/* --> */    NSLog(@\"%d\", (int)[[objA objB] retainCount]);     // 3
    NSLog(@\"%d\", (int)[[objA objB] retainCount]);     // 4
    NSLog(@\"%d\", (int)[objB retainCount]);    // 4
}

NSLog(@\"%d\", (int)[[objA objB] retainCount]);

[objA objB]