在使用FetchRequest时如何在PreviewProvider中显示示例数据

struct ResponseData: Codable {
    // 定义数据模型的属性
    // ...
}

func fetchData(completion: @escaping (Result<ResponseData, Error>) -> Void) {
    // 模拟网络请求的返回结果
    let exampleData = """
        {
            "property1": "value1",
            "property2": "value2"
        }
    """.data(using: .utf8)!
    
    do {
        let decoder = JSONDecoder()
        let responseData = try decoder.decode(ResponseData.self, from: exampleData)
        completion(.success(responseData))
    } catch {
        completion(.failure(error))
    }
}

struct ContentView: View {
    @State private var responseData: ResponseData?
    
    var body: some View {
        Text(responseData?.property1 ?? "Loading...")
            .onAppear {
                fetchData { result in
                    switch result {
                    case .success(let data):
                        self.responseData = data
                    case .failure(let error):
                        print("Error: \(error)")
                    }
                }
            }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}