Question

func load<T: Decodable>(_ filename: String, as type: T.Type = T.self) -> T {
    let data: Data

    guard let file = Bundle.main.url(forResource: filename, withExtension: nil)
        else {
            fatalError("Couldn't find \(filename) in main bundle.")
    }

    do {
        data = try Data(contentsOf: file)
    } catch {
        fatalError("Couldn't load \(filename) from main bundle:\n\(error)")
    }

    do {
        let decoder = JSONDecoder()
        return try decoder.decode(T.self, from: data)
    } catch {
        fatalError("Couldn't parse \(filename) as \(T.self):\n\(error)")
    }
}

load("jsonFilePath")

该函数从JSON提取数据。该“参数” type: T.Type = T.self的作用是什么？如果我删除此参数，代码仍然有效。那我需要什么呢？

Answer 1

此参数只是使用以下三种声明的助手，

1) let model: Model = self.load("Countries")
2) let model = self.load("Countries", as: Model.self)
3) let model = self.load("Countries") as Model

如果要使用第一种声明，可以将其从方法签名中删除。

此功能参数有什么用？

1 个答案: