使用单独的类在Swift中为TableView处理Alamofire响应的最佳方法是什么？ [英] What is the best way to handle response from Alamofire for a TableView in Swift using separate classes?

问题描述

我正在编写一个类来处理我的服务器请求，这些请求返回JSON以填充TableView。这是我第一次做这种事情，我很好奇在这里使用的最佳范例是什么。像委派这样的事情比使用dispatch_async更好吗？ Alamofire的响应几乎是异步的，因此我无法从中返回数据。由于我的请求是在共享环境中发生的（它存在于我创建的框架中，所以我可以在多个目标中使用它）ServerManager类，因此我需要以某种方式将其发送到TableView，但我不确定哪种最佳方式去做。

I'm writing a class to handle my server requests that return JSON to populate a TableView. This is my first time doing this sort of thing, and I was curious what is the be best paradigm to use here. Is something like delegation better than using dispatch_async? Pretty much Alamofire's response is asynchronous, so I can't return data out of it. Since my request is happening in a shared(it exists in a framework I created so I could use it in multiple targets) ServerManager class, I need to get it to the TableView some how, and I'm not sure what the best way to do that.

委派后台线程的优点是什么，反之亦然？我知道这个问题可能在这里被问到很多，但是我在搜索时似乎找不到很好的解释。

What are the pros of delegation over background threading and vice versa? I know this question probably gets asked a lot around here, but I couldn't seem to find a good explanation when I was searching.

推荐答案

ServerManager 中的方法应传递给闭包（块）。

The method in ServerManager should be passed a closure (block). This requires no delegation and no dispatches in the view controller.

class ServerManager {
    func fetchObjectsWithOptions(options: [AnyObject], completion: (items: [AnyObject], error: ErrorType?) -> Void) {
        // Use the options to setup and make the request
        // Be sure it executes on the main thread
        completion(items: items, error: nil)
        // Any finishing needed
    }
}

// ...

class MyTableViewController: UITableViewController {

    lazy var serverManager = ServerManager()
    var items: [AnyObject] = []

    override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)

        serverManager.fetchObjectsWithOptions([]) {
            items, error in

            if error == nil {
                self.items = items
                self.tableView.reloadData()
            }
        }
    }

}

---

闭包是可以分配给变量的函数。在Swift中，闭包相对简单。

---

Closures are functions which can be assigned to a variables. Closures are relatively simple in Swift. Here is a closure that takes no parameters and has a void return type.

{ () -> Void in print("foo") }

下面，变量 x 的类型签名为（）->无效，并被分配了闭包。仅通过调用函数 x（）即可执行关闭操作。

Below, the variable x has the type signature of () -> Void, and is assigned the closure. Executing the closure is done just line calling a function, x().

let x: () -> Void = { () -> Void in print("foo") }
x() // prints foo

作为函数参数传递。调用 funcWithClosure（）时，它将执行闭包。

Closures can be passed around as function parameters. When funcWithClosure() is called, it executes the closure.

func funcWithClosure(x: () -> Void) {
    x()
}

funcWithClosure({ () -> Void in print("foo") })

采用参数的闭包将参数及其类型指定为闭包类型的一部分。

Closures which take parameters have the parameters and their types specified as part of the closure type.

func funcWithClosure2(x: (string: String) -> Void) {
    x(string: "foo") // <-- parameters must be named
}

funcWithClosure2({ (string: String) -> Void in print(string) })

类型推断引擎允许您从闭包中删除类型。

The type inference engine allows you to remove the type from the closure.

funcWithClosure({ print("foo") }) // <-- No type declaration
funcWithClosure2({ string in print(string) }) // <-- Only parameter name

此外，如果闭包是最后一个参数，则不需要在闭包周围加上括号

In addition, if a closure is the last parameter, you don't need the parentheses around the closure.

funcWithClosure { print("foo") }

最后，这是一个以闭包结尾的多个参数的示例。

Finally, here is an example with multiple parameter ending with a closure.

func funcWithString(string: String, closure: (string: String) -> Void) {
    closure(string: string)
}

funcWithString("foo", closure: { (string: String) -> Void in print(string) })

或者，您可以使用不太冗长的语法。

Or, you can use the less verbose syntax.

funcWithString("foo") { string in print(string) }

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