Question

我正在寻找开发同步服务，当用户拉动刷新时会触发该服务。此同步服务将对服务器执行多个请求。每次API调用完成后，如何手动触发PromiseKit承诺？承诺的回调正在被立即召唤。

//MyViewController.swift
func refresh(sender: AnyObject){
    var promise = syncService.syncFromServer()
    promise.then{ response
        //This is called immediately, and I need it to wait until the sync is complete
        refreshControl?.endRefreshing()
        tableView.reloadData()
    }
}

//SyncService.swift
func syncFromServer() -> Promise<AsyncResult>{
    let promise = Promise(value: AsyncResult)
     var page = 1

    //Multiple API calls
    //let request1 = ...
    //let request2 = ...
    //let request3 = ...
    //How do I tell the returned promise to trigger the associated callbacks after the last API requests has been completed?

    //Another scenario I need to handle is when the amount of requests is not known ahead of time.
    while(true){
        var response = makeAnApiCall(page)

        //if the response body says no more data is available, break out of the while loop, and tell any promise callbacks to execute.
        //if(noMoreData){
        // how do I perform something like
        // promise.complete //This line needs to tell the `then` statement in `MyViewController` to execute.
        // break
        //}else{
        //  do something with response data
        //}
        page = page + 1
    }

    return promise
}

Answer 1

下面我提供了一个示例，说明在所有syncService调用运行后，如何结束刷新和更新tableView。查看有关使用'when'的PromiseKit文档。

func refresh(sender: AnyObject){
    syncService.syncFromServer().then { response in
        refreshControl?.endRefreshing()
        tableView.reloadData()
    }
}

//SyncService.swift
func syncFromServer() -> Promise<Void> {
    let request1 = methodReturningPromise1()
    let request2 = methodReturningPromise2()
    return when(fulfilled: [request1, request2])
}

private func methodReturningPromise1() -> Promise<Void> {
    return syncService.someDataCall().then { response -> Void in
        //do something here
    }
}

如何使用PromiseKit手动触发Swift 3中的Promise

1 个答案: