ios - 将 SAPOData.EntityValue 数组编码/解码到 CompositeStorage

Question

我正在使用适用于 iOS 的 SAP Cloud Platform SDK，试图弄清楚如何将 EntityValue 数组放入 CompositeStorage 中，然后将它们取出。我收到错误:

typeMismatch(Swift.Dictionary, Swift.DecodingError.Context(codingPath: [Foundation.(_PlistKey in _5692656F4C05BA2A580AE9322E9FB0A6)(stringValue: "Index 0", intValue: Optional(0)), Foundation.(_PlistKey in _5692656F4C05BA2A580AE9322E9FB0A6)(stringValue: "Index 0", intValue: Optional(0))], debugDescription: "Expected to decode Dictionary but found __NSCFData instead.", underlyingError: nil))

我正在尝试从此处的 CompositeStore 获取值:

var entities: [ExpensereportType] {
    do {
        guard let results = try Cache.shared.store.get(Array<ExpensereportType>.self, for: CollectionType.expensereport.rawValue) else {
            return []
        }
        return results
    }
    catch {
        print(error)
        return []
    }
}

它们在这里被编码:

self.service.fetchReservation(matching: query) { result, error in
    guard let result = result else { return completionHandler(error!) }

    do {
        let encodedResult = try JSONEncoder().encode(result)
        try self.store.put(encodedResult, for: CollectionType.reservation.rawValue)
    }
    catch {
        completionHandler(error)
    }
    completionHandler(nil)
}

有什么想法吗？

Answer 1

这个问题的解决方案很有趣:事实证明 JSONEncoder足够聪明，可以处理 Array<EntityValue> 中的任何一个。按原样，或者对各个项目进行 map 编码。但是，JSONDecoder自动处理顶级数组项，并由您来映射解码这些项。

工作解决方案:

// MARK: - Encode
self.service.fetchReservation(matching: query) { result, error in
        guard let result = result else {
            completionHandler(error!)
            return
        }

        do {
            let encodedResult = try JSONEncoder().encode(result)
            // try result.map { try JSONEncoder().encode($0) }   ALSO VALID
            try self.store.put(encodedResult, for: CollectionType.expensereport.rawValue)
        }
//...

// MARK: - Decode `Array<ExpensereportType>`
guard let results = try Cache.shared.store.get(Array<ExpensereportType>.self, for: CollectionType.expensereport.rawValue) else {
    return []
}
let decoder = JSONDecoder()
decoder.userInfo.updateValue(myDataService.metadata, forKey: CSDLDocument.csdlInfoKey)
return try results.map { try decoder.decode(ExpensereportType.self, from: $0)}