如何将包含两种类型变量的模型中的字典中的值转换为字符串？

我有一些数据数组，首先，我将字符串日期值转换为日期类型，然后创建一个字典，其中这些相同的日期作为键。但我需要的值不是从中获取这些日期的模型，而是一组相应的行（标题）。我怎样才能实现这个？

    static var newModels = [NewNewsRecordModel]()
    static var sortedMassWithSections = [SectionModel]()
    static var models: [NewsRecordModel]

    func translate() {
        for model in Transducer.models {
            let dateFormatter = DateFormatter()
            dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZ"
            if let date = dateFormatter.date(from: model.publishedAt) {
                let newModel = NewNewsRecordModel(title: model.title, publishedAt: date)
                Transducer.newModels.append(newModel)
            }
        }
    }
    
    func sortingByDictionaryToMass() {
        let calendar = Calendar.current
        let dict = Dictionary(grouping: Transducer.newModels) { (model) -> Date in
            let components = calendar.dateComponents([.year, .month, .day], from: model.publishedAt)
            let finalDate = calendar.date(from: components)
            return finalDate!
        }
        
        for element in dict {
            // Need to translate values from NewNewsRecordModel into String
            let sectionModel = SectionModel(sectionTitle: element.key, cell: element.value)
            Transducer.sortedMassWithSections.append(sectionModel)
            // Need to sort sortedMassWithSections by first element in two-dimensional array
        }
        
    }

struct NewNewsRecordModel {
    let title: String
    var publishedAt: Date
}

struct SectionModel {
    let sectionTitle: Date
    let cell: [NewNewsRecordModel]
}

struct NewsRecordModel {
    let title: String
    var publishedAt: String
}