如何在MQL4中获取网页的一部分？

Question

我是编程新手。我需要编写一个代码，用MQL4语言获取网页。我复制/粘贴了 WebRequest() 代码：

res = WebRequest( "GET",
                  Inv_url,
                  cookie,
                  NULL,
                  timeout,
                  post,
                  0,
                  result,
                  headers
                  );

可以下载整页。

然而我想只获得一个页面表，就像我在Excel中创建新查询一样。

Excel:

感谢您的帮助。

Answer 1

Well, honestly, not a typical task for MQL4

MQL4 started it's life as a language for an ultra-fast / near-real-time oriented code-execution platform ( a.k.a. [ MetaTrader Terminal 4 ] ).

This said, the language can handle very smart & fast register shifting, not to lose any amount of time inside the Market-event triggered data-stream-processing, cadence of which is many events inside a single millisecond, yes, many inside a single millisecond ( sometimes high number of hundreds of 'em in prime time ).

With this in focus, it comes natural, that there is literally no direct language / syntax support for any common markup-language-wrapped-{http|script}-composition and/or interaction with that.

For the first decade of it's life-cycle, the originally solid MQL4 language ( not the recent year or two _{( still a lot creeping )} New-MQL4.56789 derivative attempt to move and enforce the MQL4-domain towards the MQL5-domain, but it is another topic, sure ), had no support for any kind of interactions "outside of the MT4-box". Simply nothing, to avoid any sort of disturbances from external non-core, potentially blocking processes, that could de-stabilise the tough real-time execution loop of the platform.

---

That does not mean, one cannot extend MQL4 today to work with this

As a fast proxy solution, one may forget about MQL4-syntax ( functions et al ) and start thinking about doing the MQL4-part as usual and extend the [ MetaTrader Terminal 4 ] processes so as to become able to communicate with external ( distributed ) hosts, where ( as the easiest prototyping example ) a python process can do the job, that would otherwise be hard for MQL4.

This is exactly the approach, where one does not risk MQL4 troubles with parsing the markup-language-wrapped-{http|script}-composition to find any element(s) one needs.

This builds on python strengths in doing this very part and leaves one in just orchestrating the mutual-cooperation of such distributed-process workflow.

---

How to integrate the distributed-process workflows?

After many hundred man*years of experimenting and code-base maintenance, my choice No.1 is [ZeroMQ] or [nanomsg].

When not willing to invest one's own "blood, tears & sweat" into these or other smart distributed signalling / communications architectures, one may use as a last resort going into MQL4 WebRequest() even for integration against python-based lightweight-webServer to complete the intended processing-flow and deliver the wanted results onto MQL4-side.