确保你的类符合 UICollectionViewDelegateFlowLayout(对于 swift4)

Make sure you conform to UICollectionViewDelegateFlowLayout for your class (for swift4)

eg. class MyClass: UICollectionViewDelegateFlowLayout

在 Swift 3 之前

Prior to Swift 3

//Use for size
func collectionView(collectionView: UICollectionView,
        layout collectionViewLayout: UICollectionViewLayout,
        sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {

    }
//Use for interspacing
    func collectionView(collectionView: UICollectionView,
        layout collectionViewLayout: UICollectionViewLayout,
        minimumInteritemSpacingForSectionAtIndex section: Int) -> CGFloat {
            return 1.0
    }

    func collectionView(collectionView: UICollectionView, layout
        collectionViewLayout: UICollectionViewLayout,
        minimumLineSpacingForSectionAtIndex section: Int) -> CGFloat {
            return 1.0
    }

//对于 swift 3

// For swift 3

func collectionView(_ collectionView: UICollectionView,
                    layout collectionViewLayout: UICollectionViewLayout,
                    sizeForItemAt indexPath: IndexPath) -> CGSize {

}

func collectionView(_ collectionView: UICollectionView,
                    layout collectionViewLayout: UICollectionViewLayout,
                    minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
    return 1.0
}

func collectionView(_ collectionView: UICollectionView, layout
    collectionViewLayout: UICollectionViewLayout,
                    minimumLineSpacingForSectionAt section: Int) -> CGFloat {
    return 1.0
}

//对于 swift 4

// For swift 4

extension MyClass: UICollectionViewDelegateFlowLayout { 
        func collectionView(_ collectionView: UICollectionView,
                            layout collectionViewLayout: UICollectionViewLayout,
                            sizeForItemAt indexPath: IndexPath) -> CGSize {

        }

        func collectionView(_ collectionView: UICollectionView,
                            layout collectionViewLayout: UICollectionViewLayout,
                            minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
            return 1.0
        }

        func collectionView(_ collectionView: UICollectionView, layout
            collectionViewLayout: UICollectionViewLayout,
                            minimumLineSpacingForSectionAt section: Int) -> CGFloat {
            return 1.0
        }
    }

对 swift 3 使用与上面所示相同的代码，但只需 确保你的类符合协议 UICollectionViewDelegateFlowLayout