我正在开发一个应用程序,需要分批加载数据,即首先加载5个项目,然后再继续加载另外5个,但我无法弄清如何实现。目前,我将我的项目列表分成块,每个块包含5个项目。目前for循环只是发送请求,但我希望等待响应,然后在for循环中继续执行。
我使用Alamofire,我的代码如下。
这是我将列表分块并传递给上方的地方。
我使用Alamofire,我的代码如下。
private func requestItemsForField(items: [Item], completion: @escaping (_ measurements: Array<Measurement>?, _ success: Bool) -> ()) {
let userPackageId = UserManager.instance.selectedUserPackage.id
let params = ["userPackageId": userPackageId]
for field in fields {
let url = apiURL + "images/\(field.id)"
let queue = DispatchQueue(label: "com.response-queue", qos: .utility, attributes: [.concurrent])
Alamofire.request(url, method: .get, parameters: params, headers: headers()).responseArray(queue: queue, completionHandler: { (response: DataResponse<[Item]>) in
if let items = response.result.value as [Item]? {
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "itemsLoadedNotification"), object: nil)
completion(items, true)
}
else {
print("Request failed with error: \(response.result.error)")
completion(nil, false)
}
})
}
}
这是我将列表分块并传递给上方的地方。
private func fetchAllMeasurements(completion: @escaping (_ measurements: [Item]?, _ done: Bool) -> ()) {
let fieldSet = FieldStore.instance.data.keys
var fieldKeys = [Item]()
for field in fieldSet {
fieldKeys.append(field)
}
// Create chunks of fields to load
let fieldChunks = fieldKeys.chunkify(by: 5)
var measurementsAll = [Measurement]()
for fields in fieldChunks {
requestItemsForField(fields: fields, completion: { (measurements, success) in
if let currentMeasurement = measurements {
measurementsAll.append(contentsOf: currentMeasurement)
}
completion(measurementsAll, true)
}
})
}
}