IOS获取系统通讯录使用权限的优雅方式

CFErrorRef *error = nil;
    ABAddressBookRef addressBook = ABAddressBookCreateWithOptions(NULL, error);
    
    __block BOOL accessGranted = NO;
    // we're on iOS 6
    if (ABAddressBookRequestAccessWithCompletion != NULL)
    {
        dispatch_semaphore_t sema = dispatch_semaphore_create(0);
        ABAddressBookRequestAccessWithCompletion(addressBook, ^(bool granted, CFErrorRef error) {
            accessGranted = granted;
            dispatch_semaphore_signal(sema);
        });
        dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
    }
    else     // we're on iOS 5 or older
    {
        accessGranted = YES;
    }
    return accessGranted;

使用dispatch_semaphore_t的原因：
代码可以在用户选择同意或者拒绝后，立即执行剩下的代码，而不是直接返回。