[英]How to make synchronous http calls in angular 2
This question has already been asked here .这个问题已经在这里被问到了。 However, since the asker's application context is involved too much in the question, I couldn't understand the basics.但是由于提问者的应用上下文涉及太多,我无法理解基础知识。 For example, there is a queryArr
parameter.例如,有一个queryArr
参数。 What does it do?它有什么作用?
Anyway, I need a little bit of a guidance about how to make synchronous http calls in simplest way.无论如何,我需要一些关于如何以最简单的方式进行同步 http 调用的指导。 The solution I came up with is that one has to subscribe to observables in a "nested" order.我想出的解决方案是必须以“嵌套”顺序订阅可观察对象。 For example, there are observables ox
and oy
.例如,有可观察对象ox
和oy
。 Data of the request being called in oy
is depended on the data comes from ox
: oy
中调用的请求数据取决于来自ox
的数据:
xData: string = "";
yData: string = "";
ox.subscribe(
data => {xData = data;},
error => console.log(error),
() => {
oy.subscribe(
data => {yData = xData*data;},
error => console.log(error),
() => console.log("aaa")
);
}
);
Last time I remember (I don't do javascript much, and am a little newbie), in the scope where I subscribed to oy
, the xData
or yData
cannot be seen anymore.记得上次(javascript我做的不多,是个小菜鸟),在我订阅oy
的scope里, xData
或者yData
都看不到了。 Please correct me and point me to the right direction if I am wrong.如果我错了,请纠正我并指出正确的方向。
Is there any "fine" solution or better way to do this kind of thing?有没有“好的”解决方案或更好的方法来做这种事情?
I think that you could have a look at the flatMap
operator to execute an HTTP request, wait for its response and execute another one.我认为您可以查看flatMap
运算符来执行 HTTP 请求,等待其响应并执行另一个。
Here is a sample:这是一个示例:
executeHttp(url) {
return this.http.get(url).map(res => res.json());
}
executeRequests() {
this.executeHttp('http://...').flatMap(result => {
// result is the result of the first request
return this.executeHttp('http://...');
}).subscribe(result => {
// result is the result of the second request
});
}
If you want to have access to both results in the subscribe
method, you could leverage Observable.forkJoin
and Observable.of
:如果您想在subscribe
方法中访问这两个结果,您可以利用Observable.forkJoin
和Observable.of
:
executeRequests() {
this.executeHttp('http://...').flatMap(result => {
// result is the result of the first request
return Observable.forkJoin(
Observable.of(result),
this.executeHttp('http://...')
).subscribe(results => {
// results is an array of the results of all requests
let result1 = results[0];
let result2 = results[1];
});
}
如果您在此处编写@khushboo 并向我们展示您的函数/代码,您的问题将更容易理解。
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