[英]How to chain multiple paging request with node-apac?
I'm new to Javascript and Nodejs and I am trying to setup a server which can request multiple ItemPages from amazon-product-api via the node-apac node package. 我是Java和Nodejs的新手,我正在尝试设置一个服务器,该服务器可以通过node-apac节点包从amazon-product-api请求多个ItemPage。 So far my http server is up and running with some routes defined.
到目前为止,我的http服务器已经启动并正在运行,并定义了一些路由。 I can also request a single ItemPage.
我还可以请求一个ItemPage。 But I have trouble chaining the requests.
但是我很难链接请求。
example for theQuery: Query的示例:
var query = {
Title: theTitle,
SearchIndex: 'Books',
BrowseNodeId: '698198',
Power: 'binding:not (Kindle or Kalender)',
Sort: '-publication_date',
ResponseGroup: 'ItemAttributes,Images',
ItemPage: 1
};
the code: 编码:
AmazonWrapper.prototype.getAllPagesForQuery = function(theMethod, theQuery, theResultCallback) {
client.execute(theMethod, theQuery).then(function(theResult) {
var pageCount = theResult.result.ItemSearchResponse.Items.TotalPages;
var requests = [];
for(var i = 2; i < pageCount; i++) {
theQuery.ItemPage = i;
requests.push(client.execute(theMethod, theQuery));
}
Promise.all(requests).then(function(theResults) {
var data = theResults[0];
for(var i = 1; i < theResults.length; i++) {
var items = theResults[i].result.ItemSearchResponse.Items.Item;
data.result.ItemSearchResponse.Items.Item.concat(items);
}
theResultCallback(data);
});
});
};
As you see I want to read from the first request how many Itempages are available for my ItemSearch und create a new request for each Itempage. 如您所见,我想从第一个请求中读取多少个Itempage可供我的ItemSearch使用,并为每个Itempage创建一个新请求。 Unfortunately Promise.all(...).then() is never called.
不幸的是Promise.all(...)。then()从未被调用。
Any help is appreciated 任何帮助表示赞赏
theQuery
looks like an object. theQuery
看起来像一个对象。 As such, it is passed by pointer to when you do theQuery.ItemPage = i
and then you pass theQuery
, you're passing the same object to every single request and just overwriting the ItemPage
property on that one object. 这样,当您执行
theQuery.ItemPage = i
并随后传递theQuery
时,它将通过指针传递给您,您是将相同的对象传递给每个单个请求,而只是覆盖该对象上的ItemPage
属性。 This is unlikely to work properly. 这不太可能正常工作。
I don't know exactly what theQuery
is, but you probably need to make copy of it. 我不知道确切是什么
theQuery
,但是您可能需要复制它。
Also, you may as well return a promise from .getAllPagesForQuery()
rather than use a callback since you're already using promises. 同样,您最好从
.getAllPagesForQuery()
返回一个.getAllPagesForQuery()
而不要使用回调,因为您已经在使用.getAllPagesForQuery()
。 Error handling and chaining is a whole lot easier with promises all the way through. 通过promise,错误处理和链接非常容易。
You don't quite disclose enough code, but here's the general idea for how to fix: 您没有完全披露足够的代码,但是以下是有关解决方法的一般想法:
AmazonWrapper.prototype.getAllPagesForQuery = function(theMethod, theQuery) {
return client.execute(theMethod, theQuery).then(function(theResult) {
var pageCount = theResult.result.ItemSearchResponse.Items.TotalPages;
var requests = [];
for(var i = 2; i < pageCount; i++) {
// make unique copy of theQuery object
var newQuery = Object.assign({}, theQuery);
newQuery.ItemPage = i;
requests.push(client.execute(theMethod, newQuery));
}
return Promise.all(requests).then(function(theResults) {
var data = theResults[0];
for(var i = 1; i < theResults.length; i++) {
var items = theResults[i].result.ItemSearchResponse.Items.Item;
data.result.ItemSearchResponse.Items.Item = data.result.ItemSearchResponse.Items.Item.concat(items);
}
return data;
});
});
};
// Usage example:
obj.getAllPagesForQuery(...).then(function(data) {
// process returned data here
});
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