# MSPeekCollectionViewDelegateImplementation

# Version 3.0.0 is here! 🎉
The peeking logic is now done using a custom `UICollectionViewLayout` which makes it easier to integrate and will introduce less bugs! (And hopefully it will solve all the issues you were facing)

# Migrating from 2.0.0 to 3.0.0
I've tried to keep minimal effort to migrate from v2 to v3. Here are the steps:

1- Replace `MSPeekCollectionViewDelegateImplementation` initialization with `MSCollectionViewPeekingBehavior`

2- On your `collectionView`, call `configureForPeekingBehavior` like this:

```swift
collectionView.configureForPeekingBehavior(behavior: behavior)
```
3- Set the collection view's delegate as the view controller (Or any other class you want)

4- In the collection view delegate function `scrollViewWillEndDragging`, call the behavior's `scrollViewWillEndDragging` like this:
```swift
func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
        behavior.scrollViewWillEndDragging(scrollView, withVelocity: velocity, targetContentOffset: targetContentOffset)
}
```

5- ???

6- Profit 💰

You can check out the example for a detailed use

# Introduction

[![Build Status](https://travis-ci.org/MaherKSantina/MSPeekCollectionViewDelegateImplementation.svg?branch=master)](https://travis-ci.org/MaherKSantina/MSPeekCollectionViewDelegateImplementation)

![ezgif-2-9f7a86182f](https://user-images.githubusercontent.com/24646608/41348369-c0887714-6f4f-11e8-9231-8a86a278ee4a.gif)

Current design trends require complex designs which allow horizontal scrolling inside vertical scrolling. So to show the users that they can scroll vertically, a peeking item should be shown on the side. This library does exactly that.
I wrote this library because there's no pod that does this simple feature. Also, other libraries require me to inherit from a UICollectionViewController, which doesn't give alot of freedom if I'm inheriting from other View Controllers.

## Example

To run the example project, clone the repo, and run `pod install` from the Example directory first.

## Requirements

- XCode 11.2.1
- Swift 5

This pod will probably work on older versions of XCode but I haven't tested it.

## Installation

MSPeekCollectionViewDelegateImplementation is available through [CocoaPods](https://cocoapods.org). To install
it, simply add the following line to your Podfile:

```ruby
pod 'MSPeekCollectionViewDelegateImplementation'
```

## Usage

### Storyboard
1. Drag-Drop a `UICollectionView`

2. Set the reuse identifier for the collection view's cell to `Cell`

3. Create a reference for the collection view
```swift
@IBOutlet weak var collectionView: UICollectionView!
```

4. Bind collection view to outlet

5. Import library
```swift
import MSPeekCollectionViewDelegateImplementation
```

6. Create a variable of type `MSCollectionViewPeekingBehavior`
```swift
var behavior: MSCollectionViewPeekingBehavior!
```

7. In `viewDidLoad()`, , initialize the behavior and configure the `collectionView` for peek behavior:
```swift
behavior = MSCollectionViewPeekingBehavior()
collectionView.configureForPeekingBehavior(behavior: behavior)
```
Or you can use whatever arguments from the ones below (Can be combined together as needed):
```swift
behavior = MSCollectionViewPeekingBehavior(cellSpacing: 10)
```
```swift
behavior = MSCollectionViewPeekingBehavior(cellPeekWidth: 20)
```
```swift
//minimumItemsToScroll is the minimum number of items that can be scrolled
behavior = MSCollectionViewPeekingBehavior(minimumItemsToScroll: 1)
```
```swift
//maximumItemsToScroll is the maximum number of items that can be scrolled if the scroll distance is large
behavior = MSCollectionViewPeekingBehavior(maximumItemsToScroll: 3)
```
```swift
//numberOfItemsToShow is the number of items that will be shown at the same time.
behavior = MSCollectionViewPeekingBehavior(numberOfItemsToShow: 3)
```

![peek explanation](https://user-images.githubusercontent.com/24646608/41348656-b0ad14fc-6f50-11e8-8723-2996b016e9c9.jpg)


8. In `viewDidLoad()`, set the collection view's delegate to self:
```swift
collectionView.delegate = self
```
9. In the collection view delegate function `scrollViewWillEndDragging`, call the behavior's `scrollViewWillEndDragging` like this:
```swift
func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
        behavior.scrollViewWillEndDragging(scrollView, withVelocity: velocity, targetContentOffset: targetContentOffset)
}
```
10. Create the data source implementation as an extension for the `ViewController`
```swift
extension ViewController: UICollectionViewDataSource {
    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 4
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)
        //TODO: Configure cell
        return cell
    }
}
```

11. In `viewDidLoad()`, Set the collection view's data source to `self`
```swift
collectionView.dataSource = self
```

### Working Example

```swift
import UIKit
import MSPeekCollectionViewDelegateImplementation

class ViewController: UIViewController {
    
    @IBOutlet weak var collectionView: UICollectionView!
    var behavior = MSCollectionViewPeekingBehavior()

    override func viewDidLoad() {
        super.viewDidLoad()
        collectionView.configureForPeekingBehavior(behavior: behavior)
        collectionView.delegate = self
        collectionView.dataSource = self
    }
}

extension ViewController: UICollectionViewDataSource {
    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 4
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)
        cell.contentView.backgroundColor = UIColor.red
        return cell
    }
}

extension ViewController: UICollectionViewDelegate {
    func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
        behavior.scrollViewWillEndDragging(scrollView, withVelocity: velocity, targetContentOffset: targetContentOffset)
    }
    
    func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
        print(behavior.currentIndex)
    }
}
```

## Features
### Scrolling to a specific item
The `MSCollectionViewPeekingBehavior` now has a function to scroll to a specific index
```swift
public func scrollToItem(at index: Int, animated: Bool)
```

You can do something like:
```swift
behavior.scrollToItem(at: 1, animated: true)
```

### Listen to index changes
You can use the scroll view's delegate function to do that (Make sure you conform to `UICollectionViewDelegate`):
```swift
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
    print(behavior.currentIndex)
}
```

## Customization
### Vertical Scroll Direction
The implementation supports collection views with vertical directions and will automatically position cells correctly, you can set the scrolling and peeking to be vertical using:
```swift
delegate = MSCollectionViewPeekingBehavior(scrollDirection: .vertical)
collectionView.configureForPeekingBehavior(behavior: behavior)
```

## Author

Maher Santina, maher.santina90@gmail.com

## Sponsor

If you're liking this repo I'd really appreciate it if you sponsor me (Orange Juice) so that I can continue supporting this project. I'm also working on adding more reusable UI elements similar to this one to make developer's lives easier. Please see [my sponsor page](https://github.com/sponsors/MaherKSantina/) for more details

## Contributing

Any contribution is highly appreciated, please see [CONTRIBUTING.md](https://github.com/MaherKSantina/MSPeekCollectionViewDelegateImplementation/blob/master/CONTRIBUTING.md) for more info.

## License

MSPeekCollectionViewDelegateImplementation is available under the MIT license. See the [LICENSE](https://github.com/MaherKSantina/MSPeekCollectionViewDelegateImplementation/blob/master/LICENSE) file for more info.