使用promises递归检索分页数据 [英] Retrieve paginated data recursively using promises

问题描述

我正在使用以分页形式返回数据的函数。所以它将返回最多100个项目和一个键来检索接下来的100个项目。我想检索所有可用的项目。

I'm using a function which returns data in a paginated form. So it'll return max 100 items and a key to retrieve the next 100 items. I want to retrieve all the items available.

我如何以递归方式实现此目的？递归是一个不错的选择吗？我可以在没有递归的情况下以任何其他方式进行吗？

How do I recursively achieve this? Is recursion a good choice here? Can I do it any other way without recursion?

我使用Bluebird 3x作为承诺库。

I'm using Bluebird 3x as the promises library.

以下是我想要实现的内容：

Here is a snippet of what I'm trying to achieve:

getEndpoints(null, platformApplication)
  .then(function(allEndpoints) {
    // process on allEndpoints
  });


function getEndpoints(nextToken, platformApplication) {
  var params = {
    PlatformApplicationArn: platformApplication
  };

  if (nextToken) {
    params.NextToken = nextToken;
  }

  return sns.listEndpointsByPlatformApplicationAsync(params)
    .then(function(data) {
      if (data.NextToken) {
        // There is more data available that I want to retrieve.
        // But the problem here is that getEndpoints return a promise
        // and not the array. How do I chain this here so that 
        // in the end I get an array of all the endpoints concatenated.
        var moreEndpoints = getEndpoints(data.NextToken, platformApplication);
        moreEndpoints.push.apply(data.Endpoints, moreEndpoints);
      }

      return data.Endpoints;
    });
}

但问题是如果有更多数据需要检索（参见 if（data.NextToken）{...} ），如何将promises链接起来，以便最终获得所有端点的列表等。

But the problem is that if there is more data to be retrieved (see if (data.NextToken) { ... }), how do I chain the promises up so that in the end I get the list of all endpoints etc.

推荐答案

递归可能是获取所有端点的最简单方法。

Recursion is probably the easiest way to get all the endpoints.

function getAllEndpoints(platformApplication) {
    return getEndpoints(null, platformApplication);
}

function getEndpoints(nextToken, platformApplication, endpoints = []) {
  var params = {
    PlatformApplicationArn: platformApplication
  };

  if (nextToken) {
    params.NextToken = nextToken;
  }

  return sns.listEndpointsByPlatformApplicationAsync(params)
    .then(function(data) {
      endpoints.push.apply(endpoints, data.Endpoints);
      if (data.NextToken) {
          return getEndpoints(data.NextToken, platformApplication, endpoints);
      } else {
          return endpoints;
      }
    });
}

这篇关于使用promises递归检索分页数据的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！