How to append custom object to an array in Swift?

How to append custom class object to an array in Swift? Below is my code, but it shows error.

Error:

"Cannot assign value of '()' to type [PhotoVC]"

Code:

var photoVCs = [PhotoVC]()
for index in 0 ..< photos.count {
    if let vc = getPhotoController(index) {
        photoVCs = photoVCs.append(vc)
    }
}

func getPhotoController(index: Int) -> PhotoVC? {
    if index < 0 || index == NSNotFound {
        return nil
    }
    else if index == photos.count {
        return nil
    }

    let PhotoVCID = "PhotoVCID"
    if let storyboard = storyboard,
        pageVC = storyboard.instantiateViewControllerWithIdentifier(PhotoVCID) as? PhotoVC {
        pageVC.photoName = photos[index]
        pageVC.photoIndex = index
        return pageVC
    }
    return nil
}

I should be able to do it, but what's the problem?