构建列表与导航 章节 编译报错

[williewangwei]

构建列表与导航 章节 编译报错

[WillieWangWei]

1. 查看 ../SwiftUI-Tutorials-master/SwiftUI-Essentials/Models/Data.swift 文件是否存在并且引入到了工程中。

2. 查看 Data.swift 文件中 ImageStore 相关的代码是否正常，即：

final class ImageStore {
    typealias _ImageDictionary = [String: CGImage]
    fileprivate var images: _ImageDictionary = [:]

    fileprivate static var scale = 2
    
    static var shared = ImageStore()
    
    func image(name: String) -> Image {
        let index = _guaranteeImage(name: name)
        
        return Image(images.values[index], scale: CGFloat(ImageStore.scale), label: Text(verbatim: name))
    }

    static func loadImage(name: String) -> CGImage {
        guard
            let url = Bundle.main.url(forResource: name, withExtension: "jpg"),
            let imageSource = CGImageSourceCreateWithURL(url as NSURL, nil),
            let image = CGImageSourceCreateImageAtIndex(imageSource, 0, nil)
        else {
            fatalError("Couldn't load image \(name).jpg from main bundle.")
        }
        return image
    }
    
    fileprivate func _guaranteeImage(name: String) -> _ImageDictionary.Index {
        if let index = images.index(forKey: name) { return index }
        
        images[name] = ImageStore.loadImage(name: name)
        return images.index(forKey: name)!
    }
}