UICollectionView在快速單元測試中出隊引發異常

Question

我試圖用swift測試UICollectionViewDataSource，但在嘗試出隊時發生異常。異常看起來好像它沒有註冊重用標識符的類。在我的故事板我註冊類和標識，所以當我運行應用程序工作正常，但我想在隔離

// CollectionViewDataSource.swift 
import UIKit 

class CollectionViewDataSource : NSObject, UICollectionViewDataSource { 

    private var items = [MediaItem]() 

    init(items: [MediaItem]) { 
     self.items = items 
    } 

    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int { 
    return self.items.count 
    } 

    func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int { 
    return 1 
    } 

    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell { 

    let cell = collectionView.dequeueReusableCellWithReuseIdentifier("Cell", forIndexPath: indexPath) as MediaItemCell 

     // .. cell property setting 

     return cell 
    } 

} 

測試文件來測試

// CollectionViewDataSourceTests.swift 
import UIKit 
import XCTest 

class CollectionViewDataSourceTests: XCTestCase { 

    var dataSource: CollectionViewDataSource! 
    var collectionView: UICollectionView? 

    override func setUp() { 
     super.setUp() 

     let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout() 
     let size = CGRect(x: 0, y: 0, width: 100, height: 100) 
     collectionView = UICollectionView(frame: size, collectionViewLayout: layout) 

     let movieA = Movie(title: "Title", year: 1980, slug: "", banner: "") 
     let movieB = Movie(title: "", year: 1980, slug: "", banner: "") 
     let items = [movieA, movieB] 
     dataSource = CollectionViewDataSource(items: items) 

    } 

    // This crashes when attempting to dequeue a cell. It's as if the collection 
    // view never registers the class properly 
    func testDataSourceReturnsACell() { 
    let indexPath = NSIndexPath(forItem: 0, inSection: 0) 

     // Register the cell 
     collectionView!.registerClass(MediaItemCell.self, forCellWithReuseIdentifier: "Cell") 
     let cell = dataSource.collectionView(collectionView!, cellForItemAtIndexPath: indexPath) as MediaItemCell 
     XCTAssert(cell.textLabel.text == "The Shawshank Redemption", "Data source should set cell text") 

    } 

} 

Answer 1

有趣的是，這個理由測試引發了一個例外，因爲我從未將collectionView和dataSource連接在一起。我認爲這意味着UICollectionView將不允許您在沒有數據源的情況下注冊單元格。下面的固定代碼：

func testDataSourceReturnsACell() { 
    let indexPath = NSIndexPath(forItem: 0, inSection: 0) 
    collectionView!.dataSource = dataSource // d'oh 
    collectionView!.registerClass(MediaItemCell.self, forCellWithReuseIdentifier: "Cell") 
    let cell = dataSource.collectionView(collectionView!, cellForItemAtIndexPath: indexPath) as MediaItemCell 
    XCTAssert(cell.textLabel.text == "The Shawshank Redemption", "Data source should set cell text") 
}