Customised delegate 自定义代理

The example is for nesting a smallCollectionVIew into a BigCollectionViewCell, whose collection view is constructed in BigCollectionViewController. Going tomanipulate bigCollectionView in one VC through clicking cell of smallCollectionView in another class.

1. Delegate definition

    Where: BigCollectionViewCell.swift (which file you want to call a delegate function)

    protocol BigCategoryCellDelegate :class {

        func didSelectSmallCell (#indexPath:NSIndexPath)

    }

2. Create delegate property

    Where:BigCollectionViewCell.swift (a property of BigCollectionViewCell class)

    weakvar delegate: BigCategoryCellDelegate?

3. Function call

    Where:BigCollectionViewCell.swift (collectionView = smallCollectionVIew)

    func collectionView(collectionView:UICollectionView, didSelectItemAtIndexPath indexPath:NSIndexPath) {

        self.delegate?.didSelectSmallCell(indexPath: indexPath)

    }

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4. Inherit the delegate

    where: BigCollectionViewController.swift (whose property you want to manipulate)

    class BigCollectionViewController: UIViewController, ..., BigCategoryCellDelegate {}

5. Link the delegate

    where:BigCollectionViewController.swift (right after the BigCollectionViewCell() is dequeued)

    var cell = collectionView.dequeueReusableCellWithReuseIdentifier("bigCollectionViewCell", forIndexPath: indexPath) as? BigCollectionViewCell

    cell?.delegate =self

6. Function Definition

    where:BigCollectionViewController.swift

    func didSelectSmallCell (#indexPath:NSIndexPath){

        ...

        bigCollectionView?.reloadData()

    }